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) |
| GO:0005739 mitochondrion | 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). | |
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Download this section (compressed HTML)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.
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