PMPCB encodes the catalytic beta subunit of the mitochondrial processing peptidase (MPP), a Zn2+-dependent metalloendopeptidase in the mitochondrial matrix that cleaves N-terminal targeting presequences from newly imported mitochondrial precursor proteins.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
|
GO:0004222
metalloendopeptidase activity
|
IBA
GO_REF:0000033 |
ACCEPT |
Summary: Correct and core. PMPCB is the catalytic Zn2+-dependent metalloendopeptidase subunit of MPP.
Supporting Evidence:
file:human/PMPCB/PMPCB-deep-research-falcon.md
The UniProt accession **O75439** corresponds to **human PMPCB** (gene name **PMPCB**, synonym **MPPB**) annotated as **mitochondrial-processing peptidase subunit beta** (MPPβ), a member of the **peptidase M16 family** and the **catalytic β subunit** of the heterodimeric mitochondrial processing peptidase (MPP). This mapping (human PMPCB ↔ UniProt O75439) is explicitly supported by a review of mitochondrial processing peptidases that lists **Homo sapiens O75439** as the MPP subunit containing the characteristic inverted Zn-binding motif HxxEH…E required for activity, as well as by authoritative reviews describing human MPP as PMPCA (α) + PMPCB (β) with PMPCB harboring the catalytic site. (gakh2002mitochondrialprocessingpeptidases. pages 4-6, kunova2022mitochondrialprocessingpeptidases—structure pages 2-4, gala2021mitochondrialproteasesin pages 2-5, kunova2022mitochondrialprocessingpeptidases—structure pages 4-6)
file:human/PMPCB/PMPCB-deep-research-falcon.md
MPP is a **Zn2+-dependent metalloendopeptidase**. PMPCB contains the conserved inverted Zn-binding/catalytic motif **HxxEH…E** (with the distal glutamate contributing to Zn coordination). Mutation of residues in this motif abolishes Zn binding and peptidase activity, supporting that PMPCB is the catalytic subunit. (gakh2002mitochondrialprocessingpeptidases. pages 4-6, kunova2022mitochondrialprocessingpeptidases—structure pages 2-4)
file:human/PMPCB/PMPCB-deep-research-falcon.md
Authoritative reviews converge on a model in which **PMPCB is the catalytic Zn metalloprotease** and **PMPCA contributes substrate recognition**, together enabling cleavage of a large fraction of imported mitochondrial proteins. This division of labor is supported by conserved motifs (active-site Zn-binding in β subunit), structural evidence (peptide binding in a negatively charged cavity, glycine-rich loop gating/positioning), and disease genetics demonstrating that partial disruption causes severe neurological phenotypes. (gala2021mitochondrialproteasesin pages 2-5, kunova2022mitochondrialprocessingpeptidases—structure pages 2-4, gakh2002mitochondrialprocessingpeptidases. pages 4-6)
|
|
GO:0017087
mitochondrial processing peptidase complex
|
IBA
GO_REF:0000033 |
ACCEPT |
Summary: Correct and core. PMPCB forms the mitochondrial processing peptidase heterodimer with PMPCA.
Supporting Evidence:
file:human/PMPCB/PMPCB-deep-research-falcon.md
The UniProt accession **O75439** corresponds to **human PMPCB** (gene name **PMPCB**, synonym **MPPB**) annotated as **mitochondrial-processing peptidase subunit beta** (MPPβ), a member of the **peptidase M16 family** and the **catalytic β subunit** of the heterodimeric mitochondrial processing peptidase (MPP). This mapping (human PMPCB ↔ UniProt O75439) is explicitly supported by a review of mitochondrial processing peptidases that lists **Homo sapiens O75439** as the MPP subunit containing the characteristic inverted Zn-binding motif HxxEH…E required for activity, as well as by authoritative reviews describing human MPP as PMPCA (α) + PMPCB (β) with PMPCB harboring the catalytic site. (gakh2002mitochondrialprocessingpeptidases. pages 4-6, kunova2022mitochondrialprocessingpeptidases—structure pages 2-4, gala2021mitochondrialproteasesin pages 2-5, kunova2022mitochondrialprocessingpeptidases—structure pages 4-6)
file:human/PMPCB/PMPCB-deep-research-falcon.md
| Complex membership | PMPCB forms the **MPP heterodimer** with **PMPCA (α-MPP)**; PMPCB provides catalysis, whereas PMPCA contributes substrate recognition/positioning via a glycine-rich loop and helps shape the substrate-binding cavity (kunova2022mitochondrialprocessingpeptidases—structure pages 2-4, gala2021mitochondrialproteasesin pages 2-5, kunova2022mitochondrialprocessingpeptidases—structure media e22ffe68). |
|
|
GO:0004222
metalloendopeptidase activity
|
IEA
GO_REF:0000120 |
ACCEPT |
Summary: Correct and core. PMPCB is the catalytic Zn2+-dependent metalloendopeptidase subunit of MPP.
Supporting Evidence:
file:human/PMPCB/PMPCB-deep-research-falcon.md
The UniProt accession **O75439** corresponds to **human PMPCB** (gene name **PMPCB**, synonym **MPPB**) annotated as **mitochondrial-processing peptidase subunit beta** (MPPβ), a member of the **peptidase M16 family** and the **catalytic β subunit** of the heterodimeric mitochondrial processing peptidase (MPP). This mapping (human PMPCB ↔ UniProt O75439) is explicitly supported by a review of mitochondrial processing peptidases that lists **Homo sapiens O75439** as the MPP subunit containing the characteristic inverted Zn-binding motif HxxEH…E required for activity, as well as by authoritative reviews describing human MPP as PMPCA (α) + PMPCB (β) with PMPCB harboring the catalytic site. (gakh2002mitochondrialprocessingpeptidases. pages 4-6, kunova2022mitochondrialprocessingpeptidases—structure pages 2-4, gala2021mitochondrialproteasesin pages 2-5, kunova2022mitochondrialprocessingpeptidases—structure pages 4-6)
file:human/PMPCB/PMPCB-deep-research-falcon.md
MPP is a **Zn2+-dependent metalloendopeptidase**. PMPCB contains the conserved inverted Zn-binding/catalytic motif **HxxEH…E** (with the distal glutamate contributing to Zn coordination). Mutation of residues in this motif abolishes Zn binding and peptidase activity, supporting that PMPCB is the catalytic subunit. (gakh2002mitochondrialprocessingpeptidases. pages 4-6, kunova2022mitochondrialprocessingpeptidases—structure pages 2-4)
file:human/PMPCB/PMPCB-deep-research-falcon.md
Authoritative reviews converge on a model in which **PMPCB is the catalytic Zn metalloprotease** and **PMPCA contributes substrate recognition**, together enabling cleavage of a large fraction of imported mitochondrial proteins. This division of labor is supported by conserved motifs (active-site Zn-binding in β subunit), structural evidence (peptide binding in a negatively charged cavity, glycine-rich loop gating/positioning), and disease genetics demonstrating that partial disruption causes severe neurological phenotypes. (gala2021mitochondrialproteasesin pages 2-5, kunova2022mitochondrialprocessingpeptidases—structure pages 2-4, gakh2002mitochondrialprocessingpeptidases. pages 4-6)
|
|
GO:0005759
mitochondrial matrix
|
IEA
GO_REF:0000120 |
ACCEPT |
Summary: Correct. MPP/PMPCB acts in the mitochondrial matrix after precursor import through TOM/TIM.
Supporting Evidence:
file:human/PMPCB/PMPCB-deep-research-falcon.md
PMPCB functions in the **mitochondrial matrix** as part of MPP, acting on precursors after import via TOM/TIM pathways. (gala2021mitochondrialproteasesin pages 2-5, baker2025qualitycontrolat pages 4-5)
file:human/PMPCB/PMPCB-deep-research-falcon.md
In the canonical pathway, precursors are recognized and translocated through TOM and TIM machineries, then MPP removes the N-terminal targeting presequence in the matrix. Cleaved presequences are subsequently degraded by downstream peptidases (e.g., PreP), preventing accumulation of potentially disruptive targeting peptides. (baker2025qualitycontrolat pages 4-5, gala2021mitochondrialproteasesin pages 2-5)
|
|
GO:0006508
proteolysis
|
IEA
GO_REF:0000002 |
MARK AS OVER ANNOTATED |
Summary: Correct process family but too broad. PMPCB specifically performs mitochondrial presequence processing as the catalytic MPP subunit.
Reason: Prefer metalloendopeptidase activity and protein processing/presequence-cleavage terms over generic proteolysis.
Supporting Evidence:
file:human/PMPCB/PMPCB-deep-research-falcon.md
PMPCB provides the catalytic activity of MPP, which cleaves the **N-terminal mitochondrial targeting presequence** from mitochondrial precursor proteins after their translocation into mitochondria, yielding the mature protein N-terminus (or an intermediate for further processing by other peptidases). (gala2021mitochondrialproteasesin pages 2-5, taylor2001crystalstructuresof pages 1-2, baker2025qualitycontrolat pages 5-5)
file:human/PMPCB/PMPCB-deep-research-falcon.md
Authoritative reviews converge on a model in which **PMPCB is the catalytic Zn metalloprotease** and **PMPCA contributes substrate recognition**, together enabling cleavage of a large fraction of imported mitochondrial proteins. This division of labor is supported by conserved motifs (active-site Zn-binding in β subunit), structural evidence (peptide binding in a negatively charged cavity, glycine-rich loop gating/positioning), and disease genetics demonstrating that partial disruption causes severe neurological phenotypes. (gala2021mitochondrialproteasesin pages 2-5, kunova2022mitochondrialprocessingpeptidases—structure pages 2-4, gakh2002mitochondrialprocessingpeptidases. pages 4-6)
|
|
GO:0009003
signal peptidase activity
|
IEA
GO_REF:0000003 |
ACCEPT |
Summary: Correct. PMPCB cleaves mitochondrial targeting presequences; metalloendopeptidase activity captures the catalytic class more precisely.
Supporting Evidence:
file:human/PMPCB/PMPCB-deep-research-falcon.md
Most mitochondrial proteins are nuclear-encoded, synthesized in the cytosol, and imported into mitochondria using N-terminal **mitochondrial targeting presequences** (often amphipathic, positively charged α-helices). These presequences generally must be cleaved after import for proper maturation and assembly of mitochondrial proteins. The central enzyme executing this step is the **mitochondrial processing peptidase (MPP)**. (gala2021mitochondrialproteasesin pages 2-5, kunova2022mitochondrialprocessingpeptidases—structure pages 2-4, taylor2001crystalstructuresof pages 1-2)
file:human/PMPCB/PMPCB-deep-research-falcon.md
PMPCB provides the catalytic activity of MPP, which cleaves the **N-terminal mitochondrial targeting presequence** from mitochondrial precursor proteins after their translocation into mitochondria, yielding the mature protein N-terminus (or an intermediate for further processing by other peptidases). (gala2021mitochondrialproteasesin pages 2-5, taylor2001crystalstructuresof pages 1-2, baker2025qualitycontrolat pages 5-5)
|
|
GO:0016485
protein processing
|
IEA
GO_REF:0000117 |
ACCEPT |
Summary: Correct and core. PMPCB processes newly imported mitochondrial precursor proteins by removing N-terminal targeting presequences.
Supporting Evidence:
file:human/PMPCB/PMPCB-deep-research-falcon.md
Most mitochondrial proteins are nuclear-encoded, synthesized in the cytosol, and imported into mitochondria using N-terminal **mitochondrial targeting presequences** (often amphipathic, positively charged α-helices). These presequences generally must be cleaved after import for proper maturation and assembly of mitochondrial proteins. The central enzyme executing this step is the **mitochondrial processing peptidase (MPP)**. (gala2021mitochondrialproteasesin pages 2-5, kunova2022mitochondrialprocessingpeptidases—structure pages 2-4, taylor2001crystalstructuresof pages 1-2)
file:human/PMPCB/PMPCB-deep-research-falcon.md
PMPCB provides the catalytic activity of MPP, which cleaves the **N-terminal mitochondrial targeting presequence** from mitochondrial precursor proteins after their translocation into mitochondria, yielding the mature protein N-terminus (or an intermediate for further processing by other peptidases). (gala2021mitochondrialproteasesin pages 2-5, taylor2001crystalstructuresof pages 1-2, baker2025qualitycontrolat pages 5-5)
file:human/PMPCB/PMPCB-deep-research-falcon.md
In the canonical pathway, precursors are recognized and translocated through TOM and TIM machineries, then MPP removes the N-terminal targeting presequence in the matrix. Cleaved presequences are subsequently degraded by downstream peptidases (e.g., PreP), preventing accumulation of potentially disruptive targeting peptides. (baker2025qualitycontrolat pages 4-5, gala2021mitochondrialproteasesin pages 2-5)
|
|
GO:0046872
metal ion binding
|
IEA
GO_REF:0000002 |
MARK AS OVER ANNOTATED |
Summary: Correct mechanistic feature but too generic. Zinc binding is integral to the metalloendopeptidase active site, so the enzyme activity term is more informative.
Reason: Prefer metalloendopeptidase activity over generic metal ion binding.
Supporting Evidence:
file:human/PMPCB/PMPCB-deep-research-falcon.md
MPP is a **Zn2+-dependent metalloendopeptidase**. PMPCB contains the conserved inverted Zn-binding/catalytic motif **HxxEH…E** (with the distal glutamate contributing to Zn coordination). Mutation of residues in this motif abolishes Zn binding and peptidase activity, supporting that PMPCB is the catalytic subunit. (gakh2002mitochondrialprocessingpeptidases. pages 4-6, kunova2022mitochondrialprocessingpeptidases—structure pages 2-4)
|
|
GO:0005739
mitochondrion
|
NAS
PMID:32443488 Mitochondrial Protein Quality Control Mechanisms. |
MARK AS OVER ANNOTATED |
Summary: Correct but broad. PMPCB is specifically a mitochondrial matrix MPP complex subunit.
Reason: Prefer mitochondrial matrix and mitochondrial processing peptidase complex over generic mitochondrion.
Supporting Evidence:
file:human/PMPCB/PMPCB-deep-research-falcon.md
PMPCB functions in the **mitochondrial matrix** as part of MPP, acting on precursors after import via TOM/TIM pathways. (gala2021mitochondrialproteasesin pages 2-5, baker2025qualitycontrolat pages 4-5)
file:human/PMPCB/PMPCB-deep-research-falcon.md
| Complex membership | PMPCB forms the **MPP heterodimer** with **PMPCA (α-MPP)**; PMPCB provides catalysis, whereas PMPCA contributes substrate recognition/positioning via a glycine-rich loop and helps shape the substrate-binding cavity (kunova2022mitochondrialprocessingpeptidases—structure pages 2-4, gala2021mitochondrialproteasesin pages 2-5, kunova2022mitochondrialprocessingpeptidases—structure media e22ffe68). |
|
|
GO:0017087
mitochondrial processing peptidase complex
|
NAS
PMID:32443488 Mitochondrial Protein Quality Control Mechanisms. |
ACCEPT |
Summary: Correct and core. PMPCB forms the mitochondrial processing peptidase heterodimer with PMPCA.
Supporting Evidence:
file:human/PMPCB/PMPCB-deep-research-falcon.md
The UniProt accession **O75439** corresponds to **human PMPCB** (gene name **PMPCB**, synonym **MPPB**) annotated as **mitochondrial-processing peptidase subunit beta** (MPPβ), a member of the **peptidase M16 family** and the **catalytic β subunit** of the heterodimeric mitochondrial processing peptidase (MPP). This mapping (human PMPCB ↔ UniProt O75439) is explicitly supported by a review of mitochondrial processing peptidases that lists **Homo sapiens O75439** as the MPP subunit containing the characteristic inverted Zn-binding motif HxxEH…E required for activity, as well as by authoritative reviews describing human MPP as PMPCA (α) + PMPCB (β) with PMPCB harboring the catalytic site. (gakh2002mitochondrialprocessingpeptidases. pages 4-6, kunova2022mitochondrialprocessingpeptidases—structure pages 2-4, gala2021mitochondrialproteasesin pages 2-5, kunova2022mitochondrialprocessingpeptidases—structure pages 4-6)
file:human/PMPCB/PMPCB-deep-research-falcon.md
| Complex membership | PMPCB forms the **MPP heterodimer** with **PMPCA (α-MPP)**; PMPCB provides catalysis, whereas PMPCA contributes substrate recognition/positioning via a glycine-rich loop and helps shape the substrate-binding cavity (kunova2022mitochondrialprocessingpeptidases—structure pages 2-4, gala2021mitochondrialproteasesin pages 2-5, kunova2022mitochondrialprocessingpeptidases—structure media e22ffe68). |
|
|
GO:0070585
protein localization to mitochondrion
|
NAS
PMID:32443488 Mitochondrial Protein Quality Control Mechanisms. |
MARK AS OVER ANNOTATED |
Summary: Over-annotated. PMPCB acts after protein import by cleaving targeting presequences; it is not itself the import/localization machinery.
Reason: Use protein processing and metalloendopeptidase activity rather than protein localization to mitochondrion.
Supporting Evidence:
file:human/PMPCB/PMPCB-deep-research-falcon.md
In the canonical pathway, precursors are recognized and translocated through TOM and TIM machineries, then MPP removes the N-terminal targeting presequence in the matrix. Cleaved presequences are subsequently degraded by downstream peptidases (e.g., PreP), preventing accumulation of potentially disruptive targeting peptides. (baker2025qualitycontrolat pages 4-5, gala2021mitochondrialproteasesin pages 2-5)
file:human/PMPCB/PMPCB-deep-research-falcon.md
PMPCB provides the catalytic activity of MPP, which cleaves the **N-terminal mitochondrial targeting presequence** from mitochondrial precursor proteins after their translocation into mitochondria, yielding the mature protein N-terminus (or an intermediate for further processing by other peptidases). (gala2021mitochondrialproteasesin pages 2-5, taylor2001crystalstructuresof pages 1-2, baker2025qualitycontrolat pages 5-5)
|
|
GO:0005739
mitochondrion
|
IDA
GO_REF:0000052 |
MARK AS OVER ANNOTATED |
Summary: Correct but broad. PMPCB is specifically a mitochondrial matrix MPP complex subunit.
Reason: Prefer mitochondrial matrix and mitochondrial processing peptidase complex over generic mitochondrion.
Supporting Evidence:
file:human/PMPCB/PMPCB-deep-research-falcon.md
PMPCB functions in the **mitochondrial matrix** as part of MPP, acting on precursors after import via TOM/TIM pathways. (gala2021mitochondrialproteasesin pages 2-5, baker2025qualitycontrolat pages 4-5)
file:human/PMPCB/PMPCB-deep-research-falcon.md
| Complex membership | PMPCB forms the **MPP heterodimer** with **PMPCA (α-MPP)**; PMPCB provides catalysis, whereas PMPCA contributes substrate recognition/positioning via a glycine-rich loop and helps shape the substrate-binding cavity (kunova2022mitochondrialprocessingpeptidases—structure pages 2-4, gala2021mitochondrialproteasesin pages 2-5, kunova2022mitochondrialprocessingpeptidases—structure media e22ffe68). |
|
|
GO:0006851
mitochondrial calcium ion transmembrane transport
|
TAS
Reactome:R-HSA-8949215 |
MARK AS OVER ANNOTATED |
Summary: Over-annotated. PMPCB can process proSMDT1/proEMRE, a component needed for MCU complex function, but PMPCB does not catalyze calcium transmembrane transport.
Reason: The Reactome event reflects MPP cleavage of an MCU-complex subunit precursor, not direct calcium ion transport by PMPCB.
Supporting Evidence:
Reactome:R-HSA-8949649
The mitochondrial endopeptidase PMPCA:PMPCB cleaves the transit peptide of proSMDT1 (proEMRE) yielding SMDT1 (Konig et al. 2016). Mature SMDT1 is assembled into the MCU complex where it serves to bridge the MCU pore and the MCU regulators MICU1 and MICU2 (or MICU3 in neurons).
file:human/PMPCB/PMPCB-deep-research-falcon.md
PMPCB provides the catalytic activity of MPP, which cleaves the **N-terminal mitochondrial targeting presequence** from mitochondrial precursor proteins after their translocation into mitochondria, yielding the mature protein N-terminus (or an intermediate for further processing by other peptidases). (gala2021mitochondrialproteasesin pages 2-5, taylor2001crystalstructuresof pages 1-2, baker2025qualitycontrolat pages 5-5)
|
|
GO:0004222
metalloendopeptidase activity
|
TAS
Reactome:R-HSA-8949649 |
ACCEPT |
Summary: Correct and core. PMPCB is the catalytic Zn2+-dependent metalloendopeptidase subunit of MPP.
Supporting Evidence:
file:human/PMPCB/PMPCB-deep-research-falcon.md
The UniProt accession **O75439** corresponds to **human PMPCB** (gene name **PMPCB**, synonym **MPPB**) annotated as **mitochondrial-processing peptidase subunit beta** (MPPβ), a member of the **peptidase M16 family** and the **catalytic β subunit** of the heterodimeric mitochondrial processing peptidase (MPP). This mapping (human PMPCB ↔ UniProt O75439) is explicitly supported by a review of mitochondrial processing peptidases that lists **Homo sapiens O75439** as the MPP subunit containing the characteristic inverted Zn-binding motif HxxEH…E required for activity, as well as by authoritative reviews describing human MPP as PMPCA (α) + PMPCB (β) with PMPCB harboring the catalytic site. (gakh2002mitochondrialprocessingpeptidases. pages 4-6, kunova2022mitochondrialprocessingpeptidases—structure pages 2-4, gala2021mitochondrialproteasesin pages 2-5, kunova2022mitochondrialprocessingpeptidases—structure pages 4-6)
file:human/PMPCB/PMPCB-deep-research-falcon.md
MPP is a **Zn2+-dependent metalloendopeptidase**. PMPCB contains the conserved inverted Zn-binding/catalytic motif **HxxEH…E** (with the distal glutamate contributing to Zn coordination). Mutation of residues in this motif abolishes Zn binding and peptidase activity, supporting that PMPCB is the catalytic subunit. (gakh2002mitochondrialprocessingpeptidases. pages 4-6, kunova2022mitochondrialprocessingpeptidases—structure pages 2-4)
file:human/PMPCB/PMPCB-deep-research-falcon.md
Authoritative reviews converge on a model in which **PMPCB is the catalytic Zn metalloprotease** and **PMPCA contributes substrate recognition**, together enabling cleavage of a large fraction of imported mitochondrial proteins. This division of labor is supported by conserved motifs (active-site Zn-binding in β subunit), structural evidence (peptide binding in a negatively charged cavity, glycine-rich loop gating/positioning), and disease genetics demonstrating that partial disruption causes severe neurological phenotypes. (gala2021mitochondrialproteasesin pages 2-5, kunova2022mitochondrialprocessingpeptidases—structure pages 2-4, gakh2002mitochondrialprocessingpeptidases. pages 4-6)
|
|
GO:0009003
signal peptidase activity
|
ISS
GO_REF:0000024 |
ACCEPT |
Summary: Correct. PMPCB cleaves mitochondrial targeting presequences; metalloendopeptidase activity captures the catalytic class more precisely.
Supporting Evidence:
file:human/PMPCB/PMPCB-deep-research-falcon.md
Most mitochondrial proteins are nuclear-encoded, synthesized in the cytosol, and imported into mitochondria using N-terminal **mitochondrial targeting presequences** (often amphipathic, positively charged α-helices). These presequences generally must be cleaved after import for proper maturation and assembly of mitochondrial proteins. The central enzyme executing this step is the **mitochondrial processing peptidase (MPP)**. (gala2021mitochondrialproteasesin pages 2-5, kunova2022mitochondrialprocessingpeptidases—structure pages 2-4, taylor2001crystalstructuresof pages 1-2)
file:human/PMPCB/PMPCB-deep-research-falcon.md
PMPCB provides the catalytic activity of MPP, which cleaves the **N-terminal mitochondrial targeting presequence** from mitochondrial precursor proteins after their translocation into mitochondria, yielding the mature protein N-terminus (or an intermediate for further processing by other peptidases). (gala2021mitochondrialproteasesin pages 2-5, taylor2001crystalstructuresof pages 1-2, baker2025qualitycontrolat pages 5-5)
|
|
GO:0016485
protein processing
|
IDA
PMID:22354088 Mitochondrial processing peptidase regulates PINK1 processin... |
ACCEPT |
Summary: Correct and core. PMPCB processes newly imported mitochondrial precursor proteins by removing N-terminal targeting presequences.
Supporting Evidence:
file:human/PMPCB/PMPCB-deep-research-falcon.md
Most mitochondrial proteins are nuclear-encoded, synthesized in the cytosol, and imported into mitochondria using N-terminal **mitochondrial targeting presequences** (often amphipathic, positively charged α-helices). These presequences generally must be cleaved after import for proper maturation and assembly of mitochondrial proteins. The central enzyme executing this step is the **mitochondrial processing peptidase (MPP)**. (gala2021mitochondrialproteasesin pages 2-5, kunova2022mitochondrialprocessingpeptidases—structure pages 2-4, taylor2001crystalstructuresof pages 1-2)
file:human/PMPCB/PMPCB-deep-research-falcon.md
PMPCB provides the catalytic activity of MPP, which cleaves the **N-terminal mitochondrial targeting presequence** from mitochondrial precursor proteins after their translocation into mitochondria, yielding the mature protein N-terminus (or an intermediate for further processing by other peptidases). (gala2021mitochondrialproteasesin pages 2-5, taylor2001crystalstructuresof pages 1-2, baker2025qualitycontrolat pages 5-5)
file:human/PMPCB/PMPCB-deep-research-falcon.md
In the canonical pathway, precursors are recognized and translocated through TOM and TIM machineries, then MPP removes the N-terminal targeting presequence in the matrix. Cleaved presequences are subsequently degraded by downstream peptidases (e.g., PreP), preventing accumulation of potentially disruptive targeting peptides. (baker2025qualitycontrolat pages 4-5, gala2021mitochondrialproteasesin pages 2-5)
|
|
GO:0005739
mitochondrion
|
HTP
PMID:34800366 Quantitative high-confidence human mitochondrial proteome an... |
MARK AS OVER ANNOTATED |
Summary: Correct but broad. PMPCB is specifically a mitochondrial matrix MPP complex subunit.
Reason: Prefer mitochondrial matrix and mitochondrial processing peptidase complex over generic mitochondrion.
Supporting Evidence:
file:human/PMPCB/PMPCB-deep-research-falcon.md
PMPCB functions in the **mitochondrial matrix** as part of MPP, acting on precursors after import via TOM/TIM pathways. (gala2021mitochondrialproteasesin pages 2-5, baker2025qualitycontrolat pages 4-5)
file:human/PMPCB/PMPCB-deep-research-falcon.md
| Complex membership | PMPCB forms the **MPP heterodimer** with **PMPCA (α-MPP)**; PMPCB provides catalysis, whereas PMPCA contributes substrate recognition/positioning via a glycine-rich loop and helps shape the substrate-binding cavity (kunova2022mitochondrialprocessingpeptidases—structure pages 2-4, gala2021mitochondrialproteasesin pages 2-5, kunova2022mitochondrialprocessingpeptidases—structure media e22ffe68). |
|
|
GO:0005759
mitochondrial matrix
|
EXP
PMID:22354088 Mitochondrial processing peptidase regulates PINK1 processin... |
ACCEPT |
Summary: Correct. MPP/PMPCB acts in the mitochondrial matrix after precursor import through TOM/TIM.
Supporting Evidence:
file:human/PMPCB/PMPCB-deep-research-falcon.md
PMPCB functions in the **mitochondrial matrix** as part of MPP, acting on precursors after import via TOM/TIM pathways. (gala2021mitochondrialproteasesin pages 2-5, baker2025qualitycontrolat pages 4-5)
file:human/PMPCB/PMPCB-deep-research-falcon.md
In the canonical pathway, precursors are recognized and translocated through TOM and TIM machineries, then MPP removes the N-terminal targeting presequence in the matrix. Cleaved presequences are subsequently degraded by downstream peptidases (e.g., PreP), preventing accumulation of potentially disruptive targeting peptides. (baker2025qualitycontrolat pages 4-5, gala2021mitochondrialproteasesin pages 2-5)
|
|
GO:0005759
mitochondrial matrix
|
TAS
Reactome:R-HSA-8949649 |
ACCEPT |
Summary: Correct. MPP/PMPCB acts in the mitochondrial matrix after precursor import through TOM/TIM.
Supporting Evidence:
file:human/PMPCB/PMPCB-deep-research-falcon.md
PMPCB functions in the **mitochondrial matrix** as part of MPP, acting on precursors after import via TOM/TIM pathways. (gala2021mitochondrialproteasesin pages 2-5, baker2025qualitycontrolat pages 4-5)
file:human/PMPCB/PMPCB-deep-research-falcon.md
In the canonical pathway, precursors are recognized and translocated through TOM and TIM machineries, then MPP removes the N-terminal targeting presequence in the matrix. Cleaved presequences are subsequently degraded by downstream peptidases (e.g., PreP), preventing accumulation of potentially disruptive targeting peptides. (baker2025qualitycontrolat pages 4-5, gala2021mitochondrialproteasesin pages 2-5)
|
|
GO:0004222
metalloendopeptidase activity
|
IDA
PMID:22354088 Mitochondrial processing peptidase regulates PINK1 processin... |
ACCEPT |
Summary: Correct and core. PMPCB is the catalytic Zn2+-dependent metalloendopeptidase subunit of MPP.
Supporting Evidence:
file:human/PMPCB/PMPCB-deep-research-falcon.md
The UniProt accession **O75439** corresponds to **human PMPCB** (gene name **PMPCB**, synonym **MPPB**) annotated as **mitochondrial-processing peptidase subunit beta** (MPPβ), a member of the **peptidase M16 family** and the **catalytic β subunit** of the heterodimeric mitochondrial processing peptidase (MPP). This mapping (human PMPCB ↔ UniProt O75439) is explicitly supported by a review of mitochondrial processing peptidases that lists **Homo sapiens O75439** as the MPP subunit containing the characteristic inverted Zn-binding motif HxxEH…E required for activity, as well as by authoritative reviews describing human MPP as PMPCA (α) + PMPCB (β) with PMPCB harboring the catalytic site. (gakh2002mitochondrialprocessingpeptidases. pages 4-6, kunova2022mitochondrialprocessingpeptidases—structure pages 2-4, gala2021mitochondrialproteasesin pages 2-5, kunova2022mitochondrialprocessingpeptidases—structure pages 4-6)
file:human/PMPCB/PMPCB-deep-research-falcon.md
MPP is a **Zn2+-dependent metalloendopeptidase**. PMPCB contains the conserved inverted Zn-binding/catalytic motif **HxxEH…E** (with the distal glutamate contributing to Zn coordination). Mutation of residues in this motif abolishes Zn binding and peptidase activity, supporting that PMPCB is the catalytic subunit. (gakh2002mitochondrialprocessingpeptidases. pages 4-6, kunova2022mitochondrialprocessingpeptidases—structure pages 2-4)
file:human/PMPCB/PMPCB-deep-research-falcon.md
Authoritative reviews converge on a model in which **PMPCB is the catalytic Zn metalloprotease** and **PMPCA contributes substrate recognition**, together enabling cleavage of a large fraction of imported mitochondrial proteins. This division of labor is supported by conserved motifs (active-site Zn-binding in β subunit), structural evidence (peptide binding in a negatively charged cavity, glycine-rich loop gating/positioning), and disease genetics demonstrating that partial disruption causes severe neurological phenotypes. (gala2021mitochondrialproteasesin pages 2-5, kunova2022mitochondrialprocessingpeptidases—structure pages 2-4, gakh2002mitochondrialprocessingpeptidases. pages 4-6)
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GO:0005739
mitochondrion
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IDA
PMID:22354088 Mitochondrial processing peptidase regulates PINK1 processin... |
MARK AS OVER ANNOTATED |
Summary: Correct but broad. PMPCB is specifically a mitochondrial matrix MPP complex subunit.
Reason: Prefer mitochondrial matrix and mitochondrial processing peptidase complex over generic mitochondrion.
Supporting Evidence:
file:human/PMPCB/PMPCB-deep-research-falcon.md
PMPCB functions in the **mitochondrial matrix** as part of MPP, acting on precursors after import via TOM/TIM pathways. (gala2021mitochondrialproteasesin pages 2-5, baker2025qualitycontrolat pages 4-5)
file:human/PMPCB/PMPCB-deep-research-falcon.md
| Complex membership | PMPCB forms the **MPP heterodimer** with **PMPCA (α-MPP)**; PMPCB provides catalysis, whereas PMPCA contributes substrate recognition/positioning via a glycine-rich loop and helps shape the substrate-binding cavity (kunova2022mitochondrialprocessingpeptidases—structure pages 2-4, gala2021mitochondrialproteasesin pages 2-5, kunova2022mitochondrialprocessingpeptidases—structure media e22ffe68). |
|
Q: Which PMPCB disease variants primarily reduce catalytic activity versus MPP complex stability or substrate recognition?
Q: Which human MPP substrates are most sensitive to partial PMPCB impairment in neuronal cells?
Experiment: Perform quantitative N-terminomics and targeted substrate immunoblots in PMPCB-variant rescue cells to compare cleavage efficiency across mitochondrial precursors.
Hypothesis: PMPCB disease variants cause selective substrate-processing defects rather than uniform loss of all MPP cleavage.
Experiment: Separate acute PMPCB catalytic inhibition from mature EMRE rescue and measure proSMDT1 processing, MCU complex assembly, and mitochondrial calcium uptake.
Hypothesis: The PMPCB contribution to mitochondrial calcium uptake is indirect through proSMDT1/proEMRE maturation.
The research report should be a detailed narrative explaining the function, biological processes, and localization of the gene product. Citations should be given for all claims.
You should prioritize authoritative reviews and primary scientific literature when conducting research. You can supplement
this with annotations you find in gene/protein databases, but these can be outdated or inaccurate.
We are specifically interested in the primary function of the gene - for enzymes, what reaction is catalyzed, and what is the substrate specificity? For transporters, what is the substrate? For structural proteins or adapters, what is the broader structural role? For signaling molecules, what is the role in the pathway.
We are interested in where in or outside the cell the gene product carries out its function.
We are also interested in the signaling or biochemical pathways in which the gene functions. We are less interested in broad pleiotropic effects, except where these elucidate the precise role.
Include evidence where possible. We are interested in both experimental evidence as well as inference from structure, evolution, or bioinformatic analysis. Precise studies should be prioritized over high-throughput, where available.
The UniProt accession O75439 corresponds to human PMPCB (gene name PMPCB, synonym MPPB) annotated as mitochondrial-processing peptidase subunit beta (MPPβ), a member of the peptidase M16 family and the catalytic β subunit of the heterodimeric mitochondrial processing peptidase (MPP). This mapping (human PMPCB ↔ UniProt O75439) is explicitly supported by a review of mitochondrial processing peptidases that lists Homo sapiens O75439 as the MPP subunit containing the characteristic inverted Zn-binding motif HxxEH…E required for activity, as well as by authoritative reviews describing human MPP as PMPCA (α) + PMPCB (β) with PMPCB harboring the catalytic site. (gakh2002mitochondrialprocessingpeptidases. pages 4-6, kunova2022mitochondrialprocessingpeptidases—structure pages 2-4, gala2021mitochondrialproteasesin pages 2-5, kunova2022mitochondrialprocessingpeptidases—structure pages 4-6)
Most mitochondrial proteins are nuclear-encoded, synthesized in the cytosol, and imported into mitochondria using N-terminal mitochondrial targeting presequences (often amphipathic, positively charged α-helices). These presequences generally must be cleaved after import for proper maturation and assembly of mitochondrial proteins. The central enzyme executing this step is the mitochondrial processing peptidase (MPP). (gala2021mitochondrialproteasesin pages 2-5, kunova2022mitochondrialprocessingpeptidases—structure pages 2-4, taylor2001crystalstructuresof pages 1-2)
Human MPP is a heterodimeric enzyme complex consisting of:
- PMPCA (α-MPP): primarily contributes to substrate recognition/positioning, including a glycine-rich loop implicated in engaging presequences and facilitating productive presentation to the active site.
- PMPCB (β-MPP): the catalytic Zn2+-dependent metallopeptidase subunit containing the functional active site.
These subunits form a substrate-binding cavity; both are required for efficient processing in vivo. (kunova2022mitochondrialprocessingpeptidases—structure pages 2-4, gala2021mitochondrialproteasesin pages 2-5, gakh2002mitochondrialprocessingpeptidases. pages 4-6, kunova2022mitochondrialprocessingpeptidases—structure media e22ffe68)
PMPCB provides the catalytic activity of MPP, which cleaves the N-terminal mitochondrial targeting presequence from mitochondrial precursor proteins after their translocation into mitochondria, yielding the mature protein N-terminus (or an intermediate for further processing by other peptidases). (gala2021mitochondrialproteasesin pages 2-5, taylor2001crystalstructuresof pages 1-2, baker2025qualitycontrolat pages 5-5)
MPP is a Zn2+-dependent metalloendopeptidase. PMPCB contains the conserved inverted Zn-binding/catalytic motif HxxEH…E (with the distal glutamate contributing to Zn coordination). Mutation of residues in this motif abolishes Zn binding and peptidase activity, supporting that PMPCB is the catalytic subunit. (gakh2002mitochondrialprocessingpeptidases. pages 4-6, kunova2022mitochondrialprocessingpeptidases—structure pages 2-4)
Structural and mechanistic evidence indicates a thermolysin-like mechanism: a water molecule coordinated to Zn2+ is activated (polarized/deprotonated) by a nearby glutamate acting as a general base, enabling nucleophilic attack on the scissile peptide bond carbonyl to hydrolyze the peptide bond. This architecture and mechanism are supported by crystal structures and by functional evidence that mutation of the catalytic glutamate abolishes activity. (kunova2022mitochondrialprocessingpeptidases—structure pages 2-4, taylor2001crystalstructuresof pages 3-4)
MPP recognizes diverse mitochondrial presequences but exhibits characteristic preferences:
- A frequent arginine at the −2 position relative to the cleavage site (the “R−2 motif”; also described as an arginine at position 2 of the cleavage-site motif depending on indexing conventions), supported by N-terminome analyses and structural studies.
- Additional features can include upstream basic residues and a bulky hydrophobic/aromatic residue at P1, with presequences binding in an extended conformation within a large, negatively charged cavity that favors positively charged peptides. (gala2021mitochondrialproteasesin pages 2-5, taylor2001crystalstructuresof pages 1-2, taylor2001crystalstructuresof pages 3-4, kunova2022mitochondrialprocessingpeptidases—structure pages 2-4)
Although MPP processes a large fraction of imported mitochondrial proteins, frataxin (FXN) is a well-studied substrate relevant to PMPCB biology. A yeast two-hybrid assay found FXN as a direct partner of human PMPCB; and patient-derived systems with PMPCB variants show accumulation of a frataxin processing intermediate, linking PMPCB activity to FXN maturation and downstream iron–sulfur (Fe–S) biology. (kunova2022mitochondrialprocessingpeptidases—structure pages 4-6, vogtle2018mutationsinpmpcb pages 1-2)
PMPCB functions in the mitochondrial matrix as part of MPP, acting on precursors after import via TOM/TIM pathways. (gala2021mitochondrialproteasesin pages 2-5, baker2025qualitycontrolat pages 4-5)
In the canonical pathway, precursors are recognized and translocated through TOM and TIM machineries, then MPP removes the N-terminal targeting presequence in the matrix. Cleaved presequences are subsequently degraded by downstream peptidases (e.g., PreP), preventing accumulation of potentially disruptive targeting peptides. (baker2025qualitycontrolat pages 4-5, gala2021mitochondrialproteasesin pages 2-5)
A 2024 report identified the first splice-site PMPCB variant causing disease and expanded the phenotypic spectrum to an individual surviving to age 39. The study used an exon-trapping (minigene) assay to demonstrate that the splice variant causes exon 12 skipping, supporting pathogenic loss-of-function via aberrant splicing. (Matthews et al., 2024-02; URL https://doi.org/10.1038/s10038-024-01226-9) (matthews2024leighsyndromewith pages 1-2, matthews2024leighsyndromewith pages 2-3)
The 2024 report summarized prior literature, stating that before their publication only five affected individuals had been reported (all missense variants), with onset by 12 months in each pediatric case, none achieving ambulation or speech, and 3/5 dying by age 6; dystonia/epilepsy/ataxia occurred in 4/5. These numbers provide currently available coarse epidemiologic statistics for this ultra-rare disorder. (matthews2024leighsyndromewith pages 1-2)
While not centered on PMPCB variants, recent mitochondrial proteostasis studies emphasize that impaired turnover of targeting peptides and feedback inhibition of MPP can broadly disrupt mitochondrial function, reinforcing the importance of efficient presequence processing as a systems-level node (e.g., interaction with downstream peptide-degradation machinery). (gala2021mitochondrialproteasesin pages 2-5)
Biallelic pathogenic variants in PMPCB cause a mitochondrial disease often described as a Leigh-like neurodegenerative disorder and classified as multiple mitochondrial dysfunctions syndrome 6 (MMDS6). (matthews2024leighsyndromewith pages 1-2, baker2025qualitycontrolat pages 5-5)
A 2018 American Journal of Human Genetics study reported biallelic PMPCB variants in 4 families (5 affected individuals) with early-childhood onset neurodegeneration featuring episodic regression (often illness-triggered), basal ganglia lesions, and cerebellar atrophy. The study provided multi-level mechanistic evidence linking PMPCB dysfunction to impaired mitochondrial presequence processing and mitochondrial metabolism:
- Patient cells: reduced PMPCB levels and accumulation of a frataxin processing intermediate.
- Yeast modeling (Mas1, PMPCB homolog): disease-variant modeling caused growth defects and impaired MPP processing with accumulation of precursor proteins.
- Downstream mitochondrial consequences: impairment of Fe–S cluster biogenesis and decreased activity in Fe–S-dependent respiratory-chain components and enzymes; evidence of complex I assembly perturbations and complex II activity reduction in some tissues. (Vögtle et al., 2018-04; URL https://doi.org/10.1016/j.ajhg.2018.02.014) (vogtle2018mutationsinpmpcb pages 1-2, vogtle2018mutationsinpmpcb pages 11-12)
Open Targets links PMPCB to MMDS6 and broader categories including genetic and neurodegenerative disease, reflecting curated associations and literature evidence; this supports clinical relevance but is secondary to primary patient and mechanistic studies. (OpenTargets Search: -PMPCB)
PMPCB is now an established candidate gene in mitochondrial disease and Leigh(-like) syndrome gene panels and in whole-exome/whole-genome sequencing diagnostic pipelines for neurodevelopmental regression with basal ganglia/cerebellar imaging findings, given the strong causal evidence from biallelic pathogenic variants and functional validation. The 2024 splice-variant case demonstrates direct clinical utility of combining sequencing with functional splicing assays (minigene) to interpret variants. (matthews2024leighsyndromewith pages 1-2, vogtle2018mutationsinpmpcb pages 1-2)
PMPCB/MPP activity is routinely assessed indirectly by monitoring processing states of known MPP substrates (e.g., frataxin intermediates) and by proteomics/N-terminomics strategies that infer MPP cleavage motif preferences across the mitochondrial proteome. Such applications are highlighted in reviews discussing MPP specificity and downstream degradation of presequences. (gala2021mitochondrialproteasesin pages 2-5, vogtle2018mutationsinpmpcb pages 1-2)
Authoritative reviews converge on a model in which PMPCB is the catalytic Zn metalloprotease and PMPCA contributes substrate recognition, together enabling cleavage of a large fraction of imported mitochondrial proteins. This division of labor is supported by conserved motifs (active-site Zn-binding in β subunit), structural evidence (peptide binding in a negatively charged cavity, glycine-rich loop gating/positioning), and disease genetics demonstrating that partial disruption causes severe neurological phenotypes. (gala2021mitochondrialproteasesin pages 2-5, kunova2022mitochondrialprocessingpeptidases—structure pages 2-4, gakh2002mitochondrialprocessingpeptidases. pages 4-6)
Clinical and experimental evidence suggests that disease-causing PMPCB variants can lead to selective or stress-sensitive processing defects, rather than uniform failure of all MPP substrates, which may help explain tissue specificity (neurological vulnerability) and triggers (febrile illness). The yeast model’s temperature sensitivity and the observation of pathway-specific downstream defects (notably Fe–S cluster biogenesis and respiratory chain effects) support this interpretation. (vogtle2018mutationsinpmpcb pages 11-12, vogtle2018mutationsinpmpcb pages 1-2)
A 2022 review provides figures depicting MPP architecture and sequence conservation, including the Zn2+-binding catalytic site in PMPCB and the glycine-rich loop in PMPCA, along with alignments highlighting conserved motifs and disease-associated residues. These visuals are useful for functional inference and variant interpretation. (kunova2022mitochondrialprocessingpeptidases—structure media e22ffe68, kunova2022mitochondrialprocessingpeptidases—structure media bbb4e0aa)
The following table consolidates key annotation elements—identity, function, mechanism, localization, pathway role, and disease statistics.
| Aspect | Summary |
|---|---|
| Identity | PMPCB is the human gene encoding mitochondrial-processing peptidase subunit beta (MPPβ), the catalytic β subunit of the heterodimeric mitochondrial processing peptidase; this matches UniProt O75439 and the peptidase M16 metalloprotease family assignment (kunova2022mitochondrialprocessingpeptidases—structure pages 2-4, gala2021mitochondrialproteasesin pages 2-5, gakh2002mitochondrialprocessingpeptidases. pages 4-6, kunova2022mitochondrialprocessingpeptidases—structure pages 4-6). |
| Localization | PMPCB functions in the mitochondrial matrix, where MPP cleaves N-terminal targeting presequences from newly imported nuclear-encoded mitochondrial proteins after translocation through TOM/TIM import pathways (gala2021mitochondrialproteasesin pages 2-5, baker2025qualitycontrolat pages 4-5, taylor2001crystalstructuresof pages 1-2). |
| Complex membership | PMPCB forms the MPP heterodimer with PMPCA (α-MPP); PMPCB provides catalysis, whereas PMPCA contributes substrate recognition/positioning via a glycine-rich loop and helps shape the substrate-binding cavity (kunova2022mitochondrialprocessingpeptidases—structure pages 2-4, gala2021mitochondrialproteasesin pages 2-5, kunova2022mitochondrialprocessingpeptidases—structure media e22ffe68). |
| Catalytic class & EC | MPP is a Zn²⁺-dependent metallopeptidase / metalloendopeptidase; UniProt assigns EC 3.4.24.64. Reviews explicitly identify PMPCB as the zinc metalloprotease catalytic subunit of MPP (kunova2022mitochondrialprocessingpeptidases—structure pages 2-4, gala2021mitochondrialproteasesin pages 2-5, taylor2001crystalstructuresof pages 1-2, gakh2002mitochondrialprocessingpeptidases. pages 4-6). |
| Active-site motif | PMPCB contains the conserved HxxEH…E zinc-binding/catalytic motif typical of M16 peptidases; mutating residues in this motif abolishes Zn²⁺ binding and MPP activity (kunova2022mitochondrialprocessingpeptidases—structure pages 2-4, gakh2002mitochondrialprocessingpeptidases. pages 4-6, kunova2022mitochondrialprocessingpeptidases—structure pages 4-6, kunova2022mitochondrialprocessingpeptidases—structure media e22ffe68). |
| Mechanism | Structural/mechanistic work supports a thermolysin-like hydrolytic mechanism: Zn²⁺ is coordinated by active-site residues, while a nearby glutamate activates a bound water molecule for nucleophilic attack on the scissile peptide bond; the substrate binds in an extended conformation in a negatively charged cavity (kunova2022mitochondrialprocessingpeptidases—structure pages 2-4, taylor2001crystalstructuresof pages 1-2, taylor2001crystalstructuresof pages 3-4). |
| Substrate specificity / cleavage motif | PMPCB/MPP cleaves N-terminal mitochondrial targeting presequences of imported precursor proteins. Preferred features include positively charged, amphipathic presequences and frequent Arg at the −2 position relative to the cleavage site (with related recognition patterns also involving upstream basic residues and often a bulky hydrophobic/aromatic P1 residue) (kunova2022mitochondrialprocessingpeptidases—structure pages 2-4, gala2021mitochondrialproteasesin pages 2-5, taylor2001crystalstructuresof pages 1-2, taylor2001crystalstructuresof pages 3-4). |
| Key substrates / examples | MPP processes a broad range of nuclear-encoded mitochondrial precursors; frataxin (FXN) is a well-studied example whose maturation depends on PMPCB, and impaired PMPCB function leads to accumulation of frataxin processing intermediates in patient-derived cells (kunova2022mitochondrialprocessingpeptidases—structure pages 4-6, vogtle2018mutationsinpmpcb pages 1-2). |
| Pathway context | PMPCB acts in the mitochondrial protein import and presequence-processing pathway, a core mitochondrial proteostasis step required for maturation of many matrix and inner-membrane proteins; cleaved presequences are subsequently degraded by downstream peptidases such as PreP/PITRM1 (gala2021mitochondrialproteasesin pages 2-5, baker2025qualitycontrolat pages 4-5). |
| Disease association & key stats | Biallelic PMPCB variants cause multiple mitochondrial dysfunctions syndrome 6 (MMDS6) / a Leigh-like early-childhood neurodegenerative disorder. The 2018 AJHG study reported 4 families / 5 affected individuals with episodic developmental regression, basal ganglia lesions, cerebellar atrophy, and biochemical evidence of defective presequence processing, impaired frataxin maturation, Fe–S cluster defects, and complex I/II abnormalities (vogtle2018mutationsinpmpcb pages 1-2, vogtle2018mutationsinpmpcb pages 11-12, baker2025qualitycontrolat pages 5-5, OpenTargets Search: -PMPCB). |
| Recent developments 2024 | A 2024 Journal of Human Genetics case report described the first splice-site PMPCB variant and expanded the phenotype to an adult survivor: a 39-year-old compound-heterozygous individual with childhood regression/ataxia. The paper notes that before this report only 5 individuals had been described, all with onset by 12 months, none having achieved ambulation or speech, and 3/5 dying by age 6; a minigene assay showed exon 12 skipping from the splice variant (matthews2024leighsyndromewith pages 1-2, matthews2024leighsyndromewith pages 2-3). |
Table: This table summarizes verified identity, molecular function, mechanism, localization, pathway role, and disease relevance for human PMPCB/MPPβ (UniProt O75439). It condenses foundational and recent evidence, including key 2018 mechanistic disease data and the 2024 splice-variant update.
References
(gakh2002mitochondrialprocessingpeptidases. pages 4-6): Oleksandr Gakh, Patrizia Cavadini, and Grazia Isaya. Mitochondrial processing peptidases. Biochimica et biophysica acta, 1592 1:63-77, Sep 2002. URL: https://doi.org/10.1016/s0167-4889(02)00265-3, doi:10.1016/s0167-4889(02)00265-3. This article has 583 citations.
(kunova2022mitochondrialprocessingpeptidases—structure pages 2-4): Nina Kunová, Henrieta Havalová, Gabriela Ondrovičová, Barbora Stojkovičová, Jacob A. Bauer, Vladena Bauerová-Hlinková, Vladimir Pevala, and Eva Kutejová. Mitochondrial processing peptidases—structure, function and the role in human diseases. International Journal of Molecular Sciences, 23:1297, Jan 2022. URL: https://doi.org/10.3390/ijms23031297, doi:10.3390/ijms23031297. This article has 39 citations.
(gala2021mitochondrialproteasesin pages 2-5): Maria Gomez‐Fabra Gala and Friederike‐Nora Vögtle. Mitochondrial proteases in human diseases. FEBS Letters, 595:1205-1222, Feb 2021. URL: https://doi.org/10.1002/1873-3468.14039, doi:10.1002/1873-3468.14039. This article has 51 citations and is from a peer-reviewed journal.
(kunova2022mitochondrialprocessingpeptidases—structure pages 4-6): Nina Kunová, Henrieta Havalová, Gabriela Ondrovičová, Barbora Stojkovičová, Jacob A. Bauer, Vladena Bauerová-Hlinková, Vladimir Pevala, and Eva Kutejová. Mitochondrial processing peptidases—structure, function and the role in human diseases. International Journal of Molecular Sciences, 23:1297, Jan 2022. URL: https://doi.org/10.3390/ijms23031297, doi:10.3390/ijms23031297. This article has 39 citations.
(taylor2001crystalstructuresof pages 1-2): Alexander B. Taylor, Barbara S. Smith, Sakae Kitada, Katsuhiko Kojima, Hideki Miyaura, Zbyszek Otwinowski, Akio Ito, and Johann Deisenhofer. Crystal structures of mitochondrial processing peptidase reveal the mode for specific cleavage of import signal sequences. Structure, 9 7:615-25, Jul 2001. URL: https://doi.org/10.1016/s0969-2126(01)00621-9, doi:10.1016/s0969-2126(01)00621-9. This article has 320 citations and is from a domain leading peer-reviewed journal.
(kunova2022mitochondrialprocessingpeptidases—structure media e22ffe68): Nina Kunová, Henrieta Havalová, Gabriela Ondrovičová, Barbora Stojkovičová, Jacob A. Bauer, Vladena Bauerová-Hlinková, Vladimir Pevala, and Eva Kutejová. Mitochondrial processing peptidases—structure, function and the role in human diseases. International Journal of Molecular Sciences, 23:1297, Jan 2022. URL: https://doi.org/10.3390/ijms23031297, doi:10.3390/ijms23031297. This article has 39 citations.
(baker2025qualitycontrolat pages 5-5): Megan J. Baker, Kai Qi Yek, and Diana Stojanovski. Quality control at the powerhouse: mitochondrial proteostasis dysfunction and disease. Biochemical Society Transactions, 53:1105-1117, Aug 2025. URL: https://doi.org/10.1042/bst20253044, doi:10.1042/bst20253044. This article has 3 citations and is from a peer-reviewed journal.
(taylor2001crystalstructuresof pages 3-4): Alexander B. Taylor, Barbara S. Smith, Sakae Kitada, Katsuhiko Kojima, Hideki Miyaura, Zbyszek Otwinowski, Akio Ito, and Johann Deisenhofer. Crystal structures of mitochondrial processing peptidase reveal the mode for specific cleavage of import signal sequences. Structure, 9 7:615-25, Jul 2001. URL: https://doi.org/10.1016/s0969-2126(01)00621-9, doi:10.1016/s0969-2126(01)00621-9. This article has 320 citations and is from a domain leading peer-reviewed journal.
(vogtle2018mutationsinpmpcb pages 1-2): F.-Nora Vögtle, Björn Brändl, Austin Larson, Manuela Pendziwiat, Marisa W. Friederich, Susan M. White, Alice Basinger, Cansu Kücükköse, Hiltrud Muhle, Johanna A. Jähn, Oliver Keminer, Katherine L. Helbig, Carolyn F. Delto, Lisa Myketin, Dirk Mossmann, Nils Burger, Noriko Miyake, Audrey Burnett, Andreas van Baalen, Mark A. Lovell, Naomichi Matsumoto, Maie Walsh, Hung-Chun Yu, Deepali N. Shinde, Ulrich Stephani, Johan L.K. Van Hove, Franz-Josef Müller, and Ingo Helbig. Mutations in pmpcb encoding the catalytic subunit of the mitochondrial presequence protease cause neurodegeneration in early childhood. American journal of human genetics, 102 4:557-573, Apr 2018. URL: https://doi.org/10.1016/j.ajhg.2018.02.014, doi:10.1016/j.ajhg.2018.02.014. This article has 111 citations and is from a highest quality peer-reviewed journal.
(baker2025qualitycontrolat pages 4-5): Megan J. Baker, Kai Qi Yek, and Diana Stojanovski. Quality control at the powerhouse: mitochondrial proteostasis dysfunction and disease. Biochemical Society Transactions, 53:1105-1117, Aug 2025. URL: https://doi.org/10.1042/bst20253044, doi:10.1042/bst20253044. This article has 3 citations and is from a peer-reviewed journal.
(matthews2024leighsyndromewith pages 1-2): Emma Matthews, Ella F. Whittle, Faraan Khan, Meriel McEntagart, and Christopher J. Carroll. Leigh syndrome with developmental regression and ataxia due to a novel splicing variant in the pmpcb gene. Journal of Human Genetics, 69:283-285, Feb 2024. URL: https://doi.org/10.1038/s10038-024-01226-9, doi:10.1038/s10038-024-01226-9. This article has 6 citations and is from a peer-reviewed journal.
(matthews2024leighsyndromewith pages 2-3): Emma Matthews, Ella F. Whittle, Faraan Khan, Meriel McEntagart, and Christopher J. Carroll. Leigh syndrome with developmental regression and ataxia due to a novel splicing variant in the pmpcb gene. Journal of Human Genetics, 69:283-285, Feb 2024. URL: https://doi.org/10.1038/s10038-024-01226-9, doi:10.1038/s10038-024-01226-9. This article has 6 citations and is from a peer-reviewed journal.
(vogtle2018mutationsinpmpcb pages 11-12): F.-Nora Vögtle, Björn Brändl, Austin Larson, Manuela Pendziwiat, Marisa W. Friederich, Susan M. White, Alice Basinger, Cansu Kücükköse, Hiltrud Muhle, Johanna A. Jähn, Oliver Keminer, Katherine L. Helbig, Carolyn F. Delto, Lisa Myketin, Dirk Mossmann, Nils Burger, Noriko Miyake, Audrey Burnett, Andreas van Baalen, Mark A. Lovell, Naomichi Matsumoto, Maie Walsh, Hung-Chun Yu, Deepali N. Shinde, Ulrich Stephani, Johan L.K. Van Hove, Franz-Josef Müller, and Ingo Helbig. Mutations in pmpcb encoding the catalytic subunit of the mitochondrial presequence protease cause neurodegeneration in early childhood. American journal of human genetics, 102 4:557-573, Apr 2018. URL: https://doi.org/10.1016/j.ajhg.2018.02.014, doi:10.1016/j.ajhg.2018.02.014. This article has 111 citations and is from a highest quality peer-reviewed journal.
(OpenTargets Search: -PMPCB): Open Targets Query (-PMPCB, 5 results). Buniello, A. et al. (2025). Open Targets Platform: facilitating therapeutic hypotheses building in drug discovery. Nucleic Acids Research.
(kunova2022mitochondrialprocessingpeptidases—structure media bbb4e0aa): Nina Kunová, Henrieta Havalová, Gabriela Ondrovičová, Barbora Stojkovičová, Jacob A. Bauer, Vladena Bauerová-Hlinková, Vladimir Pevala, and Eva Kutejová. Mitochondrial processing peptidases—structure, function and the role in human diseases. International Journal of Molecular Sciences, 23:1297, Jan 2022. URL: https://doi.org/10.3390/ijms23031297, doi:10.3390/ijms23031297. This article has 39 citations.
id: O75439
gene_symbol: PMPCB
product_type: PROTEIN
status: COMPLETE
taxon:
id: NCBITaxon:9606
label: Homo sapiens
description: 'PMPCB encodes the catalytic beta subunit of the mitochondrial processing peptidase (MPP), a Zn2+-dependent
metalloendopeptidase in the mitochondrial matrix that cleaves N-terminal targeting presequences from newly imported
mitochondrial precursor proteins.'
existing_annotations:
- term:
id: GO:0004222
label: metalloendopeptidase activity
evidence_type: IBA
original_reference_id: GO_REF:0000033
review:
summary: Correct and core. PMPCB is the catalytic Zn2+-dependent metalloendopeptidase subunit of MPP.
action: ACCEPT
additional_reference_ids:
- file:human/PMPCB/PMPCB-deep-research-falcon.md
supported_by:
- reference_id: file:human/PMPCB/PMPCB-deep-research-falcon.md
supporting_text: The UniProt accession **O75439** corresponds to **human PMPCB** (gene name **PMPCB**,
synonym **MPPB**) annotated as **mitochondrial-processing peptidase subunit beta** (MPPβ), a member of
the **peptidase M16 family** and the **catalytic β subunit** of the heterodimeric mitochondrial
processing peptidase (MPP). This mapping (human PMPCB ↔ UniProt O75439) is explicitly supported by a
review of mitochondrial processing peptidases that lists **Homo sapiens O75439** as the MPP subunit
containing the characteristic inverted Zn-binding motif HxxEH…E required for activity, as well as by
authoritative reviews describing human MPP as PMPCA (α) + PMPCB (β) with PMPCB harboring the catalytic
site. (gakh2002mitochondrialprocessingpeptidases. pages 4-6,
kunova2022mitochondrialprocessingpeptidases—structure pages 2-4, gala2021mitochondrialproteasesin
pages 2-5, kunova2022mitochondrialprocessingpeptidases—structure pages 4-6)
- reference_id: file:human/PMPCB/PMPCB-deep-research-falcon.md
supporting_text: MPP is a **Zn2+-dependent metalloendopeptidase**. PMPCB contains the conserved inverted
Zn-binding/catalytic motif **HxxEH…E** (with the distal glutamate contributing to Zn coordination).
Mutation of residues in this motif abolishes Zn binding and peptidase activity, supporting that PMPCB
is the catalytic subunit. (gakh2002mitochondrialprocessingpeptidases. pages 4-6,
kunova2022mitochondrialprocessingpeptidases—structure pages 2-4)
- reference_id: file:human/PMPCB/PMPCB-deep-research-falcon.md
supporting_text: Authoritative reviews converge on a model in which **PMPCB is the catalytic Zn
metalloprotease** and **PMPCA contributes substrate recognition**, together enabling cleavage of a
large fraction of imported mitochondrial proteins. This division of labor is supported by conserved
motifs (active-site Zn-binding in β subunit), structural evidence (peptide binding in a negatively
charged cavity, glycine-rich loop gating/positioning), and disease genetics demonstrating that partial
disruption causes severe neurological phenotypes. (gala2021mitochondrialproteasesin pages 2-5,
kunova2022mitochondrialprocessingpeptidases—structure pages 2-4,
gakh2002mitochondrialprocessingpeptidases. pages 4-6)
- term:
id: GO:0017087
label: mitochondrial processing peptidase complex
evidence_type: IBA
original_reference_id: GO_REF:0000033
review:
summary: Correct and core. PMPCB forms the mitochondrial processing peptidase heterodimer with PMPCA.
action: ACCEPT
additional_reference_ids:
- file:human/PMPCB/PMPCB-deep-research-falcon.md
supported_by:
- reference_id: file:human/PMPCB/PMPCB-deep-research-falcon.md
supporting_text: The UniProt accession **O75439** corresponds to **human PMPCB** (gene name **PMPCB**,
synonym **MPPB**) annotated as **mitochondrial-processing peptidase subunit beta** (MPPβ), a member of
the **peptidase M16 family** and the **catalytic β subunit** of the heterodimeric mitochondrial
processing peptidase (MPP). This mapping (human PMPCB ↔ UniProt O75439) is explicitly supported by a
review of mitochondrial processing peptidases that lists **Homo sapiens O75439** as the MPP subunit
containing the characteristic inverted Zn-binding motif HxxEH…E required for activity, as well as by
authoritative reviews describing human MPP as PMPCA (α) + PMPCB (β) with PMPCB harboring the catalytic
site. (gakh2002mitochondrialprocessingpeptidases. pages 4-6,
kunova2022mitochondrialprocessingpeptidases—structure pages 2-4, gala2021mitochondrialproteasesin
pages 2-5, kunova2022mitochondrialprocessingpeptidases—structure pages 4-6)
- reference_id: file:human/PMPCB/PMPCB-deep-research-falcon.md
supporting_text: '| Complex membership | PMPCB forms the **MPP heterodimer** with **PMPCA (α-MPP)**; PMPCB
provides catalysis, whereas PMPCA contributes substrate recognition/positioning via a glycine-rich loop
and helps shape the substrate-binding cavity (kunova2022mitochondrialprocessingpeptidases—structure pages
2-4, gala2021mitochondrialproteasesin pages 2-5, kunova2022mitochondrialprocessingpeptidases—structure media
e22ffe68). |'
- term:
id: GO:0004222
label: metalloendopeptidase activity
evidence_type: IEA
original_reference_id: GO_REF:0000120
review:
summary: Correct and core. PMPCB is the catalytic Zn2+-dependent metalloendopeptidase subunit of MPP.
action: ACCEPT
additional_reference_ids:
- file:human/PMPCB/PMPCB-deep-research-falcon.md
supported_by:
- reference_id: file:human/PMPCB/PMPCB-deep-research-falcon.md
supporting_text: The UniProt accession **O75439** corresponds to **human PMPCB** (gene name **PMPCB**,
synonym **MPPB**) annotated as **mitochondrial-processing peptidase subunit beta** (MPPβ), a member of
the **peptidase M16 family** and the **catalytic β subunit** of the heterodimeric mitochondrial
processing peptidase (MPP). This mapping (human PMPCB ↔ UniProt O75439) is explicitly supported by a
review of mitochondrial processing peptidases that lists **Homo sapiens O75439** as the MPP subunit
containing the characteristic inverted Zn-binding motif HxxEH…E required for activity, as well as by
authoritative reviews describing human MPP as PMPCA (α) + PMPCB (β) with PMPCB harboring the catalytic
site. (gakh2002mitochondrialprocessingpeptidases. pages 4-6,
kunova2022mitochondrialprocessingpeptidases—structure pages 2-4, gala2021mitochondrialproteasesin
pages 2-5, kunova2022mitochondrialprocessingpeptidases—structure pages 4-6)
- reference_id: file:human/PMPCB/PMPCB-deep-research-falcon.md
supporting_text: MPP is a **Zn2+-dependent metalloendopeptidase**. PMPCB contains the conserved inverted
Zn-binding/catalytic motif **HxxEH…E** (with the distal glutamate contributing to Zn coordination).
Mutation of residues in this motif abolishes Zn binding and peptidase activity, supporting that PMPCB
is the catalytic subunit. (gakh2002mitochondrialprocessingpeptidases. pages 4-6,
kunova2022mitochondrialprocessingpeptidases—structure pages 2-4)
- reference_id: file:human/PMPCB/PMPCB-deep-research-falcon.md
supporting_text: Authoritative reviews converge on a model in which **PMPCB is the catalytic Zn
metalloprotease** and **PMPCA contributes substrate recognition**, together enabling cleavage of a
large fraction of imported mitochondrial proteins. This division of labor is supported by conserved
motifs (active-site Zn-binding in β subunit), structural evidence (peptide binding in a negatively
charged cavity, glycine-rich loop gating/positioning), and disease genetics demonstrating that partial
disruption causes severe neurological phenotypes. (gala2021mitochondrialproteasesin pages 2-5,
kunova2022mitochondrialprocessingpeptidases—structure pages 2-4,
gakh2002mitochondrialprocessingpeptidases. pages 4-6)
- term:
id: GO:0005759
label: mitochondrial matrix
evidence_type: IEA
original_reference_id: GO_REF:0000120
review:
summary: Correct. MPP/PMPCB acts in the mitochondrial matrix after precursor import through TOM/TIM.
action: ACCEPT
additional_reference_ids:
- file:human/PMPCB/PMPCB-deep-research-falcon.md
supported_by:
- reference_id: file:human/PMPCB/PMPCB-deep-research-falcon.md
supporting_text: PMPCB functions in the **mitochondrial matrix** as part of MPP, acting on precursors
after import via TOM/TIM pathways. (gala2021mitochondrialproteasesin pages 2-5,
baker2025qualitycontrolat pages 4-5)
- reference_id: file:human/PMPCB/PMPCB-deep-research-falcon.md
supporting_text: In the canonical pathway, precursors are recognized and translocated through TOM and
TIM machineries, then MPP removes the N-terminal targeting presequence in the matrix. Cleaved
presequences are subsequently degraded by downstream peptidases (e.g., PreP), preventing accumulation
of potentially disruptive targeting peptides. (baker2025qualitycontrolat pages 4-5,
gala2021mitochondrialproteasesin pages 2-5)
- term:
id: GO:0006508
label: proteolysis
evidence_type: IEA
original_reference_id: GO_REF:0000002
review:
summary: Correct process family but too broad. PMPCB specifically performs mitochondrial presequence
processing as the catalytic MPP subunit.
action: MARK_AS_OVER_ANNOTATED
additional_reference_ids:
- file:human/PMPCB/PMPCB-deep-research-falcon.md
reason: Prefer metalloendopeptidase activity and protein processing/presequence-cleavage terms over
generic proteolysis.
supported_by:
- reference_id: file:human/PMPCB/PMPCB-deep-research-falcon.md
supporting_text: PMPCB provides the catalytic activity of MPP, which cleaves the **N-terminal
mitochondrial targeting presequence** from mitochondrial precursor proteins after their translocation
into mitochondria, yielding the mature protein N-terminus (or an intermediate for further processing
by other peptidases). (gala2021mitochondrialproteasesin pages 2-5, taylor2001crystalstructuresof pages
1-2, baker2025qualitycontrolat pages 5-5)
- reference_id: file:human/PMPCB/PMPCB-deep-research-falcon.md
supporting_text: Authoritative reviews converge on a model in which **PMPCB is the catalytic Zn
metalloprotease** and **PMPCA contributes substrate recognition**, together enabling cleavage of a
large fraction of imported mitochondrial proteins. This division of labor is supported by conserved
motifs (active-site Zn-binding in β subunit), structural evidence (peptide binding in a negatively
charged cavity, glycine-rich loop gating/positioning), and disease genetics demonstrating that partial
disruption causes severe neurological phenotypes. (gala2021mitochondrialproteasesin pages 2-5,
kunova2022mitochondrialprocessingpeptidases—structure pages 2-4,
gakh2002mitochondrialprocessingpeptidases. pages 4-6)
- term:
id: GO:0009003
label: signal peptidase activity
evidence_type: IEA
original_reference_id: GO_REF:0000003
review:
summary: Correct. PMPCB cleaves mitochondrial targeting presequences; metalloendopeptidase activity
captures the catalytic class more precisely.
action: ACCEPT
additional_reference_ids:
- file:human/PMPCB/PMPCB-deep-research-falcon.md
supported_by:
- reference_id: file:human/PMPCB/PMPCB-deep-research-falcon.md
supporting_text: Most mitochondrial proteins are nuclear-encoded, synthesized in the cytosol, and
imported into mitochondria using N-terminal **mitochondrial targeting presequences** (often
amphipathic, positively charged α-helices). These presequences generally must be cleaved after import
for proper maturation and assembly of mitochondrial proteins. The central enzyme executing this step
is the **mitochondrial processing peptidase (MPP)**. (gala2021mitochondrialproteasesin pages 2-5,
kunova2022mitochondrialprocessingpeptidases—structure pages 2-4, taylor2001crystalstructuresof pages
1-2)
- reference_id: file:human/PMPCB/PMPCB-deep-research-falcon.md
supporting_text: PMPCB provides the catalytic activity of MPP, which cleaves the **N-terminal
mitochondrial targeting presequence** from mitochondrial precursor proteins after their translocation
into mitochondria, yielding the mature protein N-terminus (or an intermediate for further processing
by other peptidases). (gala2021mitochondrialproteasesin pages 2-5, taylor2001crystalstructuresof pages
1-2, baker2025qualitycontrolat pages 5-5)
- term:
id: GO:0016485
label: protein processing
evidence_type: IEA
original_reference_id: GO_REF:0000117
review:
summary: Correct and core. PMPCB processes newly imported mitochondrial precursor proteins by removing
N-terminal targeting presequences.
action: ACCEPT
additional_reference_ids:
- file:human/PMPCB/PMPCB-deep-research-falcon.md
supported_by:
- reference_id: file:human/PMPCB/PMPCB-deep-research-falcon.md
supporting_text: Most mitochondrial proteins are nuclear-encoded, synthesized in the cytosol, and
imported into mitochondria using N-terminal **mitochondrial targeting presequences** (often
amphipathic, positively charged α-helices). These presequences generally must be cleaved after import
for proper maturation and assembly of mitochondrial proteins. The central enzyme executing this step
is the **mitochondrial processing peptidase (MPP)**. (gala2021mitochondrialproteasesin pages 2-5,
kunova2022mitochondrialprocessingpeptidases—structure pages 2-4, taylor2001crystalstructuresof pages
1-2)
- reference_id: file:human/PMPCB/PMPCB-deep-research-falcon.md
supporting_text: PMPCB provides the catalytic activity of MPP, which cleaves the **N-terminal
mitochondrial targeting presequence** from mitochondrial precursor proteins after their translocation
into mitochondria, yielding the mature protein N-terminus (or an intermediate for further processing
by other peptidases). (gala2021mitochondrialproteasesin pages 2-5, taylor2001crystalstructuresof pages
1-2, baker2025qualitycontrolat pages 5-5)
- reference_id: file:human/PMPCB/PMPCB-deep-research-falcon.md
supporting_text: In the canonical pathway, precursors are recognized and translocated through TOM and
TIM machineries, then MPP removes the N-terminal targeting presequence in the matrix. Cleaved
presequences are subsequently degraded by downstream peptidases (e.g., PreP), preventing accumulation
of potentially disruptive targeting peptides. (baker2025qualitycontrolat pages 4-5,
gala2021mitochondrialproteasesin pages 2-5)
- term:
id: GO:0046872
label: metal ion binding
evidence_type: IEA
original_reference_id: GO_REF:0000002
review:
summary: Correct mechanistic feature but too generic. Zinc binding is integral to the metalloendopeptidase
active site, so the enzyme activity term is more informative.
action: MARK_AS_OVER_ANNOTATED
additional_reference_ids:
- file:human/PMPCB/PMPCB-deep-research-falcon.md
reason: Prefer metalloendopeptidase activity over generic metal ion binding.
supported_by:
- reference_id: file:human/PMPCB/PMPCB-deep-research-falcon.md
supporting_text: MPP is a **Zn2+-dependent metalloendopeptidase**. PMPCB contains the conserved inverted
Zn-binding/catalytic motif **HxxEH…E** (with the distal glutamate contributing to Zn coordination).
Mutation of residues in this motif abolishes Zn binding and peptidase activity, supporting that PMPCB
is the catalytic subunit. (gakh2002mitochondrialprocessingpeptidases. pages 4-6,
kunova2022mitochondrialprocessingpeptidases—structure pages 2-4)
- term:
id: GO:0005739
label: mitochondrion
evidence_type: NAS
original_reference_id: PMID:32443488
review:
summary: Correct but broad. PMPCB is specifically a mitochondrial matrix MPP complex subunit.
action: MARK_AS_OVER_ANNOTATED
additional_reference_ids:
- file:human/PMPCB/PMPCB-deep-research-falcon.md
reason: Prefer mitochondrial matrix and mitochondrial processing peptidase complex over generic
mitochondrion.
supported_by:
- reference_id: file:human/PMPCB/PMPCB-deep-research-falcon.md
supporting_text: PMPCB functions in the **mitochondrial matrix** as part of MPP, acting on precursors
after import via TOM/TIM pathways. (gala2021mitochondrialproteasesin pages 2-5,
baker2025qualitycontrolat pages 4-5)
- reference_id: file:human/PMPCB/PMPCB-deep-research-falcon.md
supporting_text: '| Complex membership | PMPCB forms the **MPP heterodimer** with **PMPCA (α-MPP)**; PMPCB
provides catalysis, whereas PMPCA contributes substrate recognition/positioning via a glycine-rich loop
and helps shape the substrate-binding cavity (kunova2022mitochondrialprocessingpeptidases—structure pages
2-4, gala2021mitochondrialproteasesin pages 2-5, kunova2022mitochondrialprocessingpeptidases—structure media
e22ffe68). |'
- term:
id: GO:0017087
label: mitochondrial processing peptidase complex
evidence_type: NAS
original_reference_id: PMID:32443488
review:
summary: Correct and core. PMPCB forms the mitochondrial processing peptidase heterodimer with PMPCA.
action: ACCEPT
additional_reference_ids:
- file:human/PMPCB/PMPCB-deep-research-falcon.md
supported_by:
- reference_id: file:human/PMPCB/PMPCB-deep-research-falcon.md
supporting_text: The UniProt accession **O75439** corresponds to **human PMPCB** (gene name **PMPCB**,
synonym **MPPB**) annotated as **mitochondrial-processing peptidase subunit beta** (MPPβ), a member of
the **peptidase M16 family** and the **catalytic β subunit** of the heterodimeric mitochondrial
processing peptidase (MPP). This mapping (human PMPCB ↔ UniProt O75439) is explicitly supported by a
review of mitochondrial processing peptidases that lists **Homo sapiens O75439** as the MPP subunit
containing the characteristic inverted Zn-binding motif HxxEH…E required for activity, as well as by
authoritative reviews describing human MPP as PMPCA (α) + PMPCB (β) with PMPCB harboring the catalytic
site. (gakh2002mitochondrialprocessingpeptidases. pages 4-6,
kunova2022mitochondrialprocessingpeptidases—structure pages 2-4, gala2021mitochondrialproteasesin
pages 2-5, kunova2022mitochondrialprocessingpeptidases—structure pages 4-6)
- reference_id: file:human/PMPCB/PMPCB-deep-research-falcon.md
supporting_text: '| Complex membership | PMPCB forms the **MPP heterodimer** with **PMPCA (α-MPP)**; PMPCB
provides catalysis, whereas PMPCA contributes substrate recognition/positioning via a glycine-rich loop
and helps shape the substrate-binding cavity (kunova2022mitochondrialprocessingpeptidases—structure pages
2-4, gala2021mitochondrialproteasesin pages 2-5, kunova2022mitochondrialprocessingpeptidases—structure media
e22ffe68). |'
- term:
id: GO:0070585
label: protein localization to mitochondrion
evidence_type: NAS
original_reference_id: PMID:32443488
review:
summary: Over-annotated. PMPCB acts after protein import by cleaving targeting presequences; it is not
itself the import/localization machinery.
action: MARK_AS_OVER_ANNOTATED
additional_reference_ids:
- file:human/PMPCB/PMPCB-deep-research-falcon.md
reason: Use protein processing and metalloendopeptidase activity rather than protein localization to
mitochondrion.
supported_by:
- reference_id: file:human/PMPCB/PMPCB-deep-research-falcon.md
supporting_text: In the canonical pathway, precursors are recognized and translocated through TOM and
TIM machineries, then MPP removes the N-terminal targeting presequence in the matrix. Cleaved
presequences are subsequently degraded by downstream peptidases (e.g., PreP), preventing accumulation
of potentially disruptive targeting peptides. (baker2025qualitycontrolat pages 4-5,
gala2021mitochondrialproteasesin pages 2-5)
- reference_id: file:human/PMPCB/PMPCB-deep-research-falcon.md
supporting_text: PMPCB provides the catalytic activity of MPP, which cleaves the **N-terminal
mitochondrial targeting presequence** from mitochondrial precursor proteins after their translocation
into mitochondria, yielding the mature protein N-terminus (or an intermediate for further processing
by other peptidases). (gala2021mitochondrialproteasesin pages 2-5, taylor2001crystalstructuresof pages
1-2, baker2025qualitycontrolat pages 5-5)
- term:
id: GO:0005739
label: mitochondrion
evidence_type: IDA
original_reference_id: GO_REF:0000052
review:
summary: Correct but broad. PMPCB is specifically a mitochondrial matrix MPP complex subunit.
action: MARK_AS_OVER_ANNOTATED
additional_reference_ids:
- file:human/PMPCB/PMPCB-deep-research-falcon.md
reason: Prefer mitochondrial matrix and mitochondrial processing peptidase complex over generic
mitochondrion.
supported_by:
- reference_id: file:human/PMPCB/PMPCB-deep-research-falcon.md
supporting_text: PMPCB functions in the **mitochondrial matrix** as part of MPP, acting on precursors
after import via TOM/TIM pathways. (gala2021mitochondrialproteasesin pages 2-5,
baker2025qualitycontrolat pages 4-5)
- reference_id: file:human/PMPCB/PMPCB-deep-research-falcon.md
supporting_text: '| Complex membership | PMPCB forms the **MPP heterodimer** with **PMPCA (α-MPP)**; PMPCB
provides catalysis, whereas PMPCA contributes substrate recognition/positioning via a glycine-rich loop
and helps shape the substrate-binding cavity (kunova2022mitochondrialprocessingpeptidases—structure pages
2-4, gala2021mitochondrialproteasesin pages 2-5, kunova2022mitochondrialprocessingpeptidases—structure media
e22ffe68). |'
- term:
id: GO:0006851
label: mitochondrial calcium ion transmembrane transport
evidence_type: TAS
original_reference_id: Reactome:R-HSA-8949215
review:
summary: Over-annotated. PMPCB can process proSMDT1/proEMRE, a component needed for MCU complex function,
but PMPCB does not catalyze calcium transmembrane transport.
action: MARK_AS_OVER_ANNOTATED
additional_reference_ids:
- file:human/PMPCB/PMPCB-deep-research-falcon.md
- Reactome:R-HSA-8949649
reason: The Reactome event reflects MPP cleavage of an MCU-complex subunit precursor, not direct calcium
ion transport by PMPCB.
supported_by:
- reference_id: Reactome:R-HSA-8949649
supporting_text: The mitochondrial endopeptidase PMPCA:PMPCB cleaves the transit peptide of proSMDT1
(proEMRE) yielding SMDT1 (Konig et al. 2016). Mature SMDT1 is assembled into the MCU complex where it
serves to bridge the MCU pore and the MCU regulators MICU1 and MICU2 (or MICU3 in neurons).
- reference_id: file:human/PMPCB/PMPCB-deep-research-falcon.md
supporting_text: PMPCB provides the catalytic activity of MPP, which cleaves the **N-terminal
mitochondrial targeting presequence** from mitochondrial precursor proteins after their translocation
into mitochondria, yielding the mature protein N-terminus (or an intermediate for further processing
by other peptidases). (gala2021mitochondrialproteasesin pages 2-5, taylor2001crystalstructuresof pages
1-2, baker2025qualitycontrolat pages 5-5)
- term:
id: GO:0004222
label: metalloendopeptidase activity
evidence_type: TAS
original_reference_id: Reactome:R-HSA-8949649
review:
summary: Correct and core. PMPCB is the catalytic Zn2+-dependent metalloendopeptidase subunit of MPP.
action: ACCEPT
additional_reference_ids:
- file:human/PMPCB/PMPCB-deep-research-falcon.md
supported_by:
- reference_id: file:human/PMPCB/PMPCB-deep-research-falcon.md
supporting_text: The UniProt accession **O75439** corresponds to **human PMPCB** (gene name **PMPCB**,
synonym **MPPB**) annotated as **mitochondrial-processing peptidase subunit beta** (MPPβ), a member of
the **peptidase M16 family** and the **catalytic β subunit** of the heterodimeric mitochondrial
processing peptidase (MPP). This mapping (human PMPCB ↔ UniProt O75439) is explicitly supported by a
review of mitochondrial processing peptidases that lists **Homo sapiens O75439** as the MPP subunit
containing the characteristic inverted Zn-binding motif HxxEH…E required for activity, as well as by
authoritative reviews describing human MPP as PMPCA (α) + PMPCB (β) with PMPCB harboring the catalytic
site. (gakh2002mitochondrialprocessingpeptidases. pages 4-6,
kunova2022mitochondrialprocessingpeptidases—structure pages 2-4, gala2021mitochondrialproteasesin
pages 2-5, kunova2022mitochondrialprocessingpeptidases—structure pages 4-6)
- reference_id: file:human/PMPCB/PMPCB-deep-research-falcon.md
supporting_text: MPP is a **Zn2+-dependent metalloendopeptidase**. PMPCB contains the conserved inverted
Zn-binding/catalytic motif **HxxEH…E** (with the distal glutamate contributing to Zn coordination).
Mutation of residues in this motif abolishes Zn binding and peptidase activity, supporting that PMPCB
is the catalytic subunit. (gakh2002mitochondrialprocessingpeptidases. pages 4-6,
kunova2022mitochondrialprocessingpeptidases—structure pages 2-4)
- reference_id: file:human/PMPCB/PMPCB-deep-research-falcon.md
supporting_text: Authoritative reviews converge on a model in which **PMPCB is the catalytic Zn
metalloprotease** and **PMPCA contributes substrate recognition**, together enabling cleavage of a
large fraction of imported mitochondrial proteins. This division of labor is supported by conserved
motifs (active-site Zn-binding in β subunit), structural evidence (peptide binding in a negatively
charged cavity, glycine-rich loop gating/positioning), and disease genetics demonstrating that partial
disruption causes severe neurological phenotypes. (gala2021mitochondrialproteasesin pages 2-5,
kunova2022mitochondrialprocessingpeptidases—structure pages 2-4,
gakh2002mitochondrialprocessingpeptidases. pages 4-6)
- term:
id: GO:0009003
label: signal peptidase activity
evidence_type: ISS
original_reference_id: GO_REF:0000024
review:
summary: Correct. PMPCB cleaves mitochondrial targeting presequences; metalloendopeptidase activity
captures the catalytic class more precisely.
action: ACCEPT
additional_reference_ids:
- file:human/PMPCB/PMPCB-deep-research-falcon.md
supported_by:
- reference_id: file:human/PMPCB/PMPCB-deep-research-falcon.md
supporting_text: Most mitochondrial proteins are nuclear-encoded, synthesized in the cytosol, and
imported into mitochondria using N-terminal **mitochondrial targeting presequences** (often
amphipathic, positively charged α-helices). These presequences generally must be cleaved after import
for proper maturation and assembly of mitochondrial proteins. The central enzyme executing this step
is the **mitochondrial processing peptidase (MPP)**. (gala2021mitochondrialproteasesin pages 2-5,
kunova2022mitochondrialprocessingpeptidases—structure pages 2-4, taylor2001crystalstructuresof pages
1-2)
- reference_id: file:human/PMPCB/PMPCB-deep-research-falcon.md
supporting_text: PMPCB provides the catalytic activity of MPP, which cleaves the **N-terminal
mitochondrial targeting presequence** from mitochondrial precursor proteins after their translocation
into mitochondria, yielding the mature protein N-terminus (or an intermediate for further processing
by other peptidases). (gala2021mitochondrialproteasesin pages 2-5, taylor2001crystalstructuresof pages
1-2, baker2025qualitycontrolat pages 5-5)
- term:
id: GO:0016485
label: protein processing
evidence_type: IDA
original_reference_id: PMID:22354088
review:
summary: Correct and core. PMPCB processes newly imported mitochondrial precursor proteins by removing
N-terminal targeting presequences.
action: ACCEPT
additional_reference_ids:
- file:human/PMPCB/PMPCB-deep-research-falcon.md
supported_by:
- reference_id: file:human/PMPCB/PMPCB-deep-research-falcon.md
supporting_text: Most mitochondrial proteins are nuclear-encoded, synthesized in the cytosol, and
imported into mitochondria using N-terminal **mitochondrial targeting presequences** (often
amphipathic, positively charged α-helices). These presequences generally must be cleaved after import
for proper maturation and assembly of mitochondrial proteins. The central enzyme executing this step
is the **mitochondrial processing peptidase (MPP)**. (gala2021mitochondrialproteasesin pages 2-5,
kunova2022mitochondrialprocessingpeptidases—structure pages 2-4, taylor2001crystalstructuresof pages
1-2)
- reference_id: file:human/PMPCB/PMPCB-deep-research-falcon.md
supporting_text: PMPCB provides the catalytic activity of MPP, which cleaves the **N-terminal
mitochondrial targeting presequence** from mitochondrial precursor proteins after their translocation
into mitochondria, yielding the mature protein N-terminus (or an intermediate for further processing
by other peptidases). (gala2021mitochondrialproteasesin pages 2-5, taylor2001crystalstructuresof pages
1-2, baker2025qualitycontrolat pages 5-5)
- reference_id: file:human/PMPCB/PMPCB-deep-research-falcon.md
supporting_text: In the canonical pathway, precursors are recognized and translocated through TOM and
TIM machineries, then MPP removes the N-terminal targeting presequence in the matrix. Cleaved
presequences are subsequently degraded by downstream peptidases (e.g., PreP), preventing accumulation
of potentially disruptive targeting peptides. (baker2025qualitycontrolat pages 4-5,
gala2021mitochondrialproteasesin pages 2-5)
- term:
id: GO:0005739
label: mitochondrion
evidence_type: HTP
original_reference_id: PMID:34800366
review:
summary: Correct but broad. PMPCB is specifically a mitochondrial matrix MPP complex subunit.
action: MARK_AS_OVER_ANNOTATED
additional_reference_ids:
- file:human/PMPCB/PMPCB-deep-research-falcon.md
reason: Prefer mitochondrial matrix and mitochondrial processing peptidase complex over generic
mitochondrion.
supported_by:
- reference_id: file:human/PMPCB/PMPCB-deep-research-falcon.md
supporting_text: PMPCB functions in the **mitochondrial matrix** as part of MPP, acting on precursors
after import via TOM/TIM pathways. (gala2021mitochondrialproteasesin pages 2-5,
baker2025qualitycontrolat pages 4-5)
- reference_id: file:human/PMPCB/PMPCB-deep-research-falcon.md
supporting_text: '| Complex membership | PMPCB forms the **MPP heterodimer** with **PMPCA (α-MPP)**; PMPCB
provides catalysis, whereas PMPCA contributes substrate recognition/positioning via a glycine-rich loop
and helps shape the substrate-binding cavity (kunova2022mitochondrialprocessingpeptidases—structure pages
2-4, gala2021mitochondrialproteasesin pages 2-5, kunova2022mitochondrialprocessingpeptidases—structure media
e22ffe68). |'
- term:
id: GO:0005759
label: mitochondrial matrix
evidence_type: EXP
original_reference_id: PMID:22354088
review:
summary: Correct. MPP/PMPCB acts in the mitochondrial matrix after precursor import through TOM/TIM.
action: ACCEPT
additional_reference_ids:
- file:human/PMPCB/PMPCB-deep-research-falcon.md
supported_by:
- reference_id: file:human/PMPCB/PMPCB-deep-research-falcon.md
supporting_text: PMPCB functions in the **mitochondrial matrix** as part of MPP, acting on precursors
after import via TOM/TIM pathways. (gala2021mitochondrialproteasesin pages 2-5,
baker2025qualitycontrolat pages 4-5)
- reference_id: file:human/PMPCB/PMPCB-deep-research-falcon.md
supporting_text: In the canonical pathway, precursors are recognized and translocated through TOM and
TIM machineries, then MPP removes the N-terminal targeting presequence in the matrix. Cleaved
presequences are subsequently degraded by downstream peptidases (e.g., PreP), preventing accumulation
of potentially disruptive targeting peptides. (baker2025qualitycontrolat pages 4-5,
gala2021mitochondrialproteasesin pages 2-5)
- term:
id: GO:0005759
label: mitochondrial matrix
evidence_type: TAS
original_reference_id: Reactome:R-HSA-8949649
review:
summary: Correct. MPP/PMPCB acts in the mitochondrial matrix after precursor import through TOM/TIM.
action: ACCEPT
additional_reference_ids:
- file:human/PMPCB/PMPCB-deep-research-falcon.md
supported_by:
- reference_id: file:human/PMPCB/PMPCB-deep-research-falcon.md
supporting_text: PMPCB functions in the **mitochondrial matrix** as part of MPP, acting on precursors
after import via TOM/TIM pathways. (gala2021mitochondrialproteasesin pages 2-5,
baker2025qualitycontrolat pages 4-5)
- reference_id: file:human/PMPCB/PMPCB-deep-research-falcon.md
supporting_text: In the canonical pathway, precursors are recognized and translocated through TOM and
TIM machineries, then MPP removes the N-terminal targeting presequence in the matrix. Cleaved
presequences are subsequently degraded by downstream peptidases (e.g., PreP), preventing accumulation
of potentially disruptive targeting peptides. (baker2025qualitycontrolat pages 4-5,
gala2021mitochondrialproteasesin pages 2-5)
- term:
id: GO:0004222
label: metalloendopeptidase activity
evidence_type: IDA
original_reference_id: PMID:22354088
review:
summary: Correct and core. PMPCB is the catalytic Zn2+-dependent metalloendopeptidase subunit of MPP.
action: ACCEPT
additional_reference_ids:
- file:human/PMPCB/PMPCB-deep-research-falcon.md
supported_by:
- reference_id: file:human/PMPCB/PMPCB-deep-research-falcon.md
supporting_text: The UniProt accession **O75439** corresponds to **human PMPCB** (gene name **PMPCB**,
synonym **MPPB**) annotated as **mitochondrial-processing peptidase subunit beta** (MPPβ), a member of
the **peptidase M16 family** and the **catalytic β subunit** of the heterodimeric mitochondrial
processing peptidase (MPP). This mapping (human PMPCB ↔ UniProt O75439) is explicitly supported by a
review of mitochondrial processing peptidases that lists **Homo sapiens O75439** as the MPP subunit
containing the characteristic inverted Zn-binding motif HxxEH…E required for activity, as well as by
authoritative reviews describing human MPP as PMPCA (α) + PMPCB (β) with PMPCB harboring the catalytic
site. (gakh2002mitochondrialprocessingpeptidases. pages 4-6,
kunova2022mitochondrialprocessingpeptidases—structure pages 2-4, gala2021mitochondrialproteasesin
pages 2-5, kunova2022mitochondrialprocessingpeptidases—structure pages 4-6)
- reference_id: file:human/PMPCB/PMPCB-deep-research-falcon.md
supporting_text: MPP is a **Zn2+-dependent metalloendopeptidase**. PMPCB contains the conserved inverted
Zn-binding/catalytic motif **HxxEH…E** (with the distal glutamate contributing to Zn coordination).
Mutation of residues in this motif abolishes Zn binding and peptidase activity, supporting that PMPCB
is the catalytic subunit. (gakh2002mitochondrialprocessingpeptidases. pages 4-6,
kunova2022mitochondrialprocessingpeptidases—structure pages 2-4)
- reference_id: file:human/PMPCB/PMPCB-deep-research-falcon.md
supporting_text: Authoritative reviews converge on a model in which **PMPCB is the catalytic Zn
metalloprotease** and **PMPCA contributes substrate recognition**, together enabling cleavage of a
large fraction of imported mitochondrial proteins. This division of labor is supported by conserved
motifs (active-site Zn-binding in β subunit), structural evidence (peptide binding in a negatively
charged cavity, glycine-rich loop gating/positioning), and disease genetics demonstrating that partial
disruption causes severe neurological phenotypes. (gala2021mitochondrialproteasesin pages 2-5,
kunova2022mitochondrialprocessingpeptidases—structure pages 2-4,
gakh2002mitochondrialprocessingpeptidases. pages 4-6)
- term:
id: GO:0005739
label: mitochondrion
evidence_type: IDA
original_reference_id: PMID:22354088
review:
summary: Correct but broad. PMPCB is specifically a mitochondrial matrix MPP complex subunit.
action: MARK_AS_OVER_ANNOTATED
additional_reference_ids:
- file:human/PMPCB/PMPCB-deep-research-falcon.md
reason: Prefer mitochondrial matrix and mitochondrial processing peptidase complex over generic
mitochondrion.
supported_by:
- reference_id: file:human/PMPCB/PMPCB-deep-research-falcon.md
supporting_text: PMPCB functions in the **mitochondrial matrix** as part of MPP, acting on precursors
after import via TOM/TIM pathways. (gala2021mitochondrialproteasesin pages 2-5,
baker2025qualitycontrolat pages 4-5)
- reference_id: file:human/PMPCB/PMPCB-deep-research-falcon.md
supporting_text: '| Complex membership | PMPCB forms the **MPP heterodimer** with **PMPCA (α-MPP)**; PMPCB
provides catalysis, whereas PMPCA contributes substrate recognition/positioning via a glycine-rich loop
and helps shape the substrate-binding cavity (kunova2022mitochondrialprocessingpeptidases—structure pages
2-4, gala2021mitochondrialproteasesin pages 2-5, kunova2022mitochondrialprocessingpeptidases—structure media
e22ffe68). |'
references:
- id: GO_REF:0000002
title: Gene Ontology annotation through association of InterPro records with GO terms
findings: []
- id: GO_REF:0000003
title: Gene Ontology annotation based on Enzyme Commission mapping
findings: []
- id: GO_REF:0000024
title: Manual transfer of experimentally-verified manual GO annotation data to orthologs by curator judgment
of sequence similarity
findings: []
- id: GO_REF:0000033
title: Annotation inferences using phylogenetic trees
findings: []
- id: GO_REF:0000052
title: Gene Ontology annotation based on curation of immunofluorescence data
findings: []
- id: GO_REF:0000117
title: Electronic Gene Ontology annotations created by ARBA machine learning models
findings: []
- id: GO_REF:0000120
title: Combined Automated Annotation using Multiple IEA Methods
findings: []
- id: PMID:22354088
title: Mitochondrial processing peptidase regulates PINK1 processing, import and Parkin recruitment.
findings: []
- id: PMID:32443488
title: Mitochondrial Protein Quality Control Mechanisms.
findings: []
- id: PMID:34800366
title: Quantitative high-confidence human mitochondrial proteome and its dynamics in cellular context.
findings: []
- id: Reactome:R-HSA-8949215
title: Mitochondrial calcium ion transport
findings: []
- id: Reactome:R-HSA-8949649
title: PMPCA:PMPCB cleaves the transit peptide of proSMDT1 (proEMRE)
findings: []
- id: file:human/PMPCB/PMPCB-deep-research-falcon.md
title: Falcon deep research report for human PMPCB
findings: []
core_functions:
- description: PMPCB is the catalytic beta subunit of the mitochondrial processing peptidase heterodimer. In
the mitochondrial matrix, it performs Zn2+-dependent metalloendopeptidase cleavage of N-terminal
mitochondrial targeting presequences from imported precursor proteins.
supported_by:
- reference_id: file:human/PMPCB/PMPCB-deep-research-falcon.md
supporting_text: The UniProt accession **O75439** corresponds to **human PMPCB** (gene name **PMPCB**,
synonym **MPPB**) annotated as **mitochondrial-processing peptidase subunit beta** (MPPβ), a member of
the **peptidase M16 family** and the **catalytic β subunit** of the heterodimeric mitochondrial
processing peptidase (MPP). This mapping (human PMPCB ↔ UniProt O75439) is explicitly supported by a
review of mitochondrial processing peptidases that lists **Homo sapiens O75439** as the MPP subunit
containing the characteristic inverted Zn-binding motif HxxEH…E required for activity, as well as by
authoritative reviews describing human MPP as PMPCA (α) + PMPCB (β) with PMPCB harboring the catalytic
site. (gakh2002mitochondrialprocessingpeptidases. pages 4-6,
kunova2022mitochondrialprocessingpeptidases—structure pages 2-4, gala2021mitochondrialproteasesin pages
2-5, kunova2022mitochondrialprocessingpeptidases—structure pages 4-6)
- reference_id: file:human/PMPCB/PMPCB-deep-research-falcon.md
supporting_text: PMPCB provides the catalytic activity of MPP, which cleaves the **N-terminal
mitochondrial targeting presequence** from mitochondrial precursor proteins after their translocation
into mitochondria, yielding the mature protein N-terminus (or an intermediate for further processing by
other peptidases). (gala2021mitochondrialproteasesin pages 2-5, taylor2001crystalstructuresof pages 1-2,
baker2025qualitycontrolat pages 5-5)
- reference_id: file:human/PMPCB/PMPCB-deep-research-falcon.md
supporting_text: MPP is a **Zn2+-dependent metalloendopeptidase**. PMPCB contains the conserved inverted
Zn-binding/catalytic motif **HxxEH…E** (with the distal glutamate contributing to Zn coordination).
Mutation of residues in this motif abolishes Zn binding and peptidase activity, supporting that PMPCB is
the catalytic subunit. (gakh2002mitochondrialprocessingpeptidases. pages 4-6,
kunova2022mitochondrialprocessingpeptidases—structure pages 2-4)
- reference_id: file:human/PMPCB/PMPCB-deep-research-falcon.md
supporting_text: PMPCB functions in the **mitochondrial matrix** as part of MPP, acting on precursors
after import via TOM/TIM pathways. (gala2021mitochondrialproteasesin pages 2-5,
baker2025qualitycontrolat pages 4-5)
- reference_id: file:human/PMPCB/PMPCB-deep-research-falcon.md
supporting_text: Authoritative reviews converge on a model in which **PMPCB is the catalytic Zn
metalloprotease** and **PMPCA contributes substrate recognition**, together enabling cleavage of a large
fraction of imported mitochondrial proteins. This division of labor is supported by conserved motifs
(active-site Zn-binding in β subunit), structural evidence (peptide binding in a negatively charged
cavity, glycine-rich loop gating/positioning), and disease genetics demonstrating that partial
disruption causes severe neurological phenotypes. (gala2021mitochondrialproteasesin pages 2-5,
kunova2022mitochondrialprocessingpeptidases—structure pages 2-4,
gakh2002mitochondrialprocessingpeptidases. pages 4-6)
molecular_function:
id: GO:0004222
label: metalloendopeptidase activity
directly_involved_in:
- id: GO:0016485
label: protein processing
locations:
- id: GO:0005759
label: mitochondrial matrix
in_complex:
id: GO:0017087
label: mitochondrial processing peptidase complex
proposed_new_terms: []
suggested_questions:
- question: Which PMPCB disease variants primarily reduce catalytic activity versus MPP complex stability or
substrate recognition?
experts: []
- question: Which human MPP substrates are most sensitive to partial PMPCB impairment in neuronal cells?
experts: []
suggested_experiments:
- hypothesis: PMPCB disease variants cause selective substrate-processing defects rather than uniform loss of
all MPP cleavage.
description: Perform quantitative N-terminomics and targeted substrate immunoblots in PMPCB-variant rescue
cells to compare cleavage efficiency across mitochondrial precursors.
- hypothesis: The PMPCB contribution to mitochondrial calcium uptake is indirect through proSMDT1/proEMRE
maturation.
description: Separate acute PMPCB catalytic inhibition from mature EMRE rescue and measure proSMDT1
processing, MCU complex assembly, and mitochondrial calcium uptake.