TIMM21 encodes a non-enzymatic accessory subunit of the mitochondrial TIM23 presequence translocase. In human cells it is best supported as a TIM23SORT factor that works with ROMO1 to promote lateral insertion/sorting of selected presequence-containing proteins into the inner mitochondrial membrane, with secondary links to respiratory-chain assembly contexts through this import/sorting role.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
|
GO:0005744
TIM23 mitochondrial import inner membrane translocase complex
|
IBA
GO_REF:0000033 |
ACCEPT |
Summary: Correct. TIMM21 is a TIM23-associated accessory subunit and, with ROMO1, defines the TIM23SORT state of the TIM23 presequence translocase.
Supporting Evidence:
file:human/TIMM21/TIMM21-deep-research-falcon.md
- **TIM23SORT (lateral insertion/sorting mode):** specialized for **lateral insertion** of single- or dual-pass IMM proteins. In this mode, association with **TIMM21** and **ROMO1** defines the “sort-specific” configuration and supports lateral release of substrates into the IMM.
|
|
GO:0030150
protein import into mitochondrial matrix
|
IBA
GO_REF:0000033 |
MARK AS OVER ANNOTATED |
Summary: TIMM21 participates in the TIM23 pathway, but the best-supported human role is TIM23SORT-mediated lateral insertion into the inner membrane rather than matrix-import motor function.
Reason: Prefer TIM23 complex membership and protein insertion into mitochondrial inner membrane for TIMM21; matrix import is primarily a TIM23MOTOR/core translocase output rather than TIMM21-specific activity.
Supporting Evidence:
file:human/TIMM21/TIMM21-deep-research-falcon.md
- **TIM23SORT (lateral insertion/sorting mode):** specialized for **lateral insertion** of single- or dual-pass IMM proteins. In this mode, association with **TIMM21** and **ROMO1** defines the “sort-specific” configuration and supports lateral release of substrates into the IMM.
file:human/TIMM21/TIMM21-deep-research-falcon.md
2) **facilitates lateral insertion** of specific IMM proteins (rather than acting as an enzyme or transporter with a small-molecule substrate).
|
|
GO:0005744
TIM23 mitochondrial import inner membrane translocase complex
|
IEA
GO_REF:0000002 |
ACCEPT |
Summary: Correct. TIMM21 is a TIM23-associated accessory subunit and, with ROMO1, defines the TIM23SORT state of the TIM23 presequence translocase.
Supporting Evidence:
file:human/TIMM21/TIMM21-deep-research-falcon.md
- **TIM23SORT (lateral insertion/sorting mode):** specialized for **lateral insertion** of single- or dual-pass IMM proteins. In this mode, association with **TIMM21** and **ROMO1** defines the “sort-specific” configuration and supports lateral release of substrates into the IMM.
|
|
GO:0030150
protein import into mitochondrial matrix
|
IEA
GO_REF:0000002 |
MARK AS OVER ANNOTATED |
Summary: TIMM21 participates in the TIM23 pathway, but the best-supported human role is TIM23SORT-mediated lateral insertion into the inner membrane rather than matrix-import motor function.
Reason: Prefer TIM23 complex membership and protein insertion into mitochondrial inner membrane for TIMM21; matrix import is primarily a TIM23MOTOR/core translocase output rather than TIMM21-specific activity.
Supporting Evidence:
file:human/TIMM21/TIMM21-deep-research-falcon.md
- **TIM23SORT (lateral insertion/sorting mode):** specialized for **lateral insertion** of single- or dual-pass IMM proteins. In this mode, association with **TIMM21** and **ROMO1** defines the “sort-specific” configuration and supports lateral release of substrates into the IMM.
file:human/TIMM21/TIMM21-deep-research-falcon.md
2) **facilitates lateral insertion** of specific IMM proteins (rather than acting as an enzyme or transporter with a small-molecule substrate).
|
|
GO:0031966
mitochondrial membrane
|
IEA
GO_REF:0000044 |
MARK AS OVER ANNOTATED |
Summary: Correct but too broad. TIMM21 is specifically associated with the mitochondrial inner membrane TIM23 machinery.
Reason: Use mitochondrial inner membrane and TIM23 complex annotations instead of generic mitochondrial membrane.
Supporting Evidence:
file:human/TIMM21/TIMM21-deep-research-falcon.md
- **Cellular location:** mitochondria, associated with the **inner mitochondrial membrane** as part of TIM23-related assemblies. (crameri2024reducedproteinimport pages 1-3)
|
|
GO:0005515
protein binding
|
IPI
PMID:23260140 MITRAC links mitochondrial protein translocation to respirat... |
MARK AS OVER ANNOTATED |
Summary: Protein binding is too generic for TIMM21. The informative biology is TIM23SORT/TIM23-complex association with ROMO1/TIM23 machinery rather than undifferentiated binding.
Reason: Replace generic protein binding interpretation with specific TIM23 complex and TIM23SORT functional context.
Supporting Evidence:
file:human/TIMM21/TIMM21-deep-research-falcon.md
- **TIM23SORT (lateral insertion/sorting mode):** specialized for **lateral insertion** of single- or dual-pass IMM proteins. In this mode, association with **TIMM21** and **ROMO1** defines the “sort-specific” configuration and supports lateral release of substrates into the IMM.
|
|
GO:0005515
protein binding
|
IPI
PMID:32296183 A reference map of the human binary protein interactome. |
MARK AS OVER ANNOTATED |
Summary: Protein binding is too generic for TIMM21. The informative biology is TIM23SORT/TIM23-complex association with ROMO1/TIM23 machinery rather than undifferentiated binding.
Reason: Replace generic protein binding interpretation with specific TIM23 complex and TIM23SORT functional context.
Supporting Evidence:
file:human/TIMM21/TIMM21-deep-research-falcon.md
- **TIM23SORT (lateral insertion/sorting mode):** specialized for **lateral insertion** of single- or dual-pass IMM proteins. In this mode, association with **TIMM21** and **ROMO1** defines the “sort-specific” configuration and supports lateral release of substrates into the IMM.
|
|
GO:0005743
mitochondrial inner membrane
|
NAS
PMID:10339406 Genetic and structural characterization of the human mitocho... |
ACCEPT |
Summary: Correct. TIMM21 is associated with the mitochondrial inner membrane as part of TIM23-related assemblies.
Supporting Evidence:
file:human/TIMM21/TIMM21-deep-research-falcon.md
- **Cellular location:** mitochondria, associated with the **inner mitochondrial membrane** as part of TIM23-related assemblies. (crameri2024reducedproteinimport pages 1-3)
|
|
GO:0005744
TIM23 mitochondrial import inner membrane translocase complex
|
NAS
PMID:10339406 Genetic and structural characterization of the human mitocho... |
ACCEPT |
Summary: Correct. TIMM21 is a TIM23-associated accessory subunit and, with ROMO1, defines the TIM23SORT state of the TIM23 presequence translocase.
Supporting Evidence:
file:human/TIMM21/TIMM21-deep-research-falcon.md
- **TIM23SORT (lateral insertion/sorting mode):** specialized for **lateral insertion** of single- or dual-pass IMM proteins. In this mode, association with **TIMM21** and **ROMO1** defines the “sort-specific” configuration and supports lateral release of substrates into the IMM.
|
|
GO:0006886
intracellular protein transport
|
NAS
PMID:10339406 Genetic and structural characterization of the human mitocho... |
MARK AS OVER ANNOTATED |
Summary: Correct pathway family but too broad. TIMM21 is specifically involved in TIM23SORT-mediated mitochondrial inner-membrane protein insertion/sorting.
Reason: Use specific mitochondrial protein import/sorting terms and TIM23 complex annotation rather than generic intracellular protein transport.
Supporting Evidence:
file:human/TIMM21/TIMM21-deep-research-falcon.md
- **TIM23SORT (lateral insertion/sorting mode):** specialized for **lateral insertion** of single- or dual-pass IMM proteins. In this mode, association with **TIMM21** and **ROMO1** defines the “sort-specific” configuration and supports lateral release of substrates into the IMM.
file:human/TIMM21/TIMM21-deep-research-falcon.md
2) **facilitates lateral insertion** of specific IMM proteins (rather than acting as an enzyme or transporter with a small-molecule substrate).
|
|
GO:0005739
mitochondrion
|
HTP
PMID:34800366 Quantitative high-confidence human mitochondrial proteome an... |
MARK AS OVER ANNOTATED |
Summary: Correct but broad. TIMM21 is better captured by mitochondrial inner membrane and TIM23 complex annotations.
Reason: Prefer mitochondrial inner membrane/TIM23 complex over generic mitochondrion.
Supporting Evidence:
file:human/TIMM21/TIMM21-deep-research-falcon.md
- **Cellular location:** mitochondria, associated with the **inner mitochondrial membrane** as part of TIM23-related assemblies. (crameri2024reducedproteinimport pages 1-3)
|
|
GO:0005758
mitochondrial intermembrane space
|
TAS
Reactome:R-HSA-9865412 |
ACCEPT |
Summary: Supported as TIMM21 function at the inner-membrane/intermembrane-space interface during TOM-TIM23 handover, not as a soluble IMS protein.
Supporting Evidence:
file:human/TIMM21/TIMM21-deep-research-falcon.md
In this framework, **Tim21** is discussed as participating in TOM–TIM23 contact-site biology and regulating early transfer steps through the intermembrane space (IMS), though much of this detailed mechanistic evidence is rooted in yeast/conserved systems and then extrapolated to mammals.
|
|
GO:0005758
mitochondrial intermembrane space
|
TAS
Reactome:R-HSA-9865579 |
ACCEPT |
Summary: Supported as TIMM21 function at the inner-membrane/intermembrane-space interface during TOM-TIM23 handover, not as a soluble IMS protein.
Supporting Evidence:
file:human/TIMM21/TIMM21-deep-research-falcon.md
In this framework, **Tim21** is discussed as participating in TOM–TIM23 contact-site biology and regulating early transfer steps through the intermembrane space (IMS), though much of this detailed mechanistic evidence is rooted in yeast/conserved systems and then extrapolated to mammals.
|
|
GO:0005744
TIM23 mitochondrial import inner membrane translocase complex
|
IDA
PMID:30598479 ROMO1 is a constituent of the human presequence translocase ... |
ACCEPT |
Summary: Correct. TIMM21 is a TIM23-associated accessory subunit and, with ROMO1, defines the TIM23SORT state of the TIM23 presequence translocase.
Supporting Evidence:
file:human/TIMM21/TIMM21-deep-research-falcon.md
- **TIM23SORT (lateral insertion/sorting mode):** specialized for **lateral insertion** of single- or dual-pass IMM proteins. In this mode, association with **TIMM21** and **ROMO1** defines the “sort-specific” configuration and supports lateral release of substrates into the IMM.
|
|
GO:0005515
protein binding
|
IPI
PMID:26321642 MITRAC7 Acts as a COX1-Specific Chaperone and Reveals a Chec... |
MARK AS OVER ANNOTATED |
Summary: Protein binding is too generic for TIMM21. The informative biology is TIM23SORT/TIM23-complex association with ROMO1/TIM23 machinery rather than undifferentiated binding.
Reason: Replace generic protein binding interpretation with specific TIM23 complex and TIM23SORT functional context.
Supporting Evidence:
file:human/TIMM21/TIMM21-deep-research-falcon.md
- **TIM23SORT (lateral insertion/sorting mode):** specialized for **lateral insertion** of single- or dual-pass IMM proteins. In this mode, association with **TIMM21** and **ROMO1** defines the “sort-specific” configuration and supports lateral release of substrates into the IMM.
|
|
GO:0005743
mitochondrial inner membrane
|
TAS
Reactome:R-HSA-9865412 |
ACCEPT |
Summary: Correct. TIMM21 is associated with the mitochondrial inner membrane as part of TIM23-related assemblies.
Supporting Evidence:
file:human/TIMM21/TIMM21-deep-research-falcon.md
- **Cellular location:** mitochondria, associated with the **inner mitochondrial membrane** as part of TIM23-related assemblies. (crameri2024reducedproteinimport pages 1-3)
|
|
GO:0005743
mitochondrial inner membrane
|
TAS
Reactome:R-HSA-9865449 |
ACCEPT |
Summary: Correct. TIMM21 is associated with the mitochondrial inner membrane as part of TIM23-related assemblies.
Supporting Evidence:
file:human/TIMM21/TIMM21-deep-research-falcon.md
- **Cellular location:** mitochondria, associated with the **inner mitochondrial membrane** as part of TIM23-related assemblies. (crameri2024reducedproteinimport pages 1-3)
|
|
GO:0005743
mitochondrial inner membrane
|
TAS
Reactome:R-HSA-9865579 |
ACCEPT |
Summary: Correct. TIMM21 is associated with the mitochondrial inner membrane as part of TIM23-related assemblies.
Supporting Evidence:
file:human/TIMM21/TIMM21-deep-research-falcon.md
- **Cellular location:** mitochondria, associated with the **inner mitochondrial membrane** as part of TIM23-related assemblies. (crameri2024reducedproteinimport pages 1-3)
|
|
GO:0005744
TIM23 mitochondrial import inner membrane translocase complex
|
IDA
PMID:23260140 MITRAC links mitochondrial protein translocation to respirat... |
ACCEPT |
Summary: Correct. TIMM21 is a TIM23-associated accessory subunit and, with ROMO1, defines the TIM23SORT state of the TIM23 presequence translocase.
Supporting Evidence:
file:human/TIMM21/TIMM21-deep-research-falcon.md
- **TIM23SORT (lateral insertion/sorting mode):** specialized for **lateral insertion** of single- or dual-pass IMM proteins. In this mode, association with **TIMM21** and **ROMO1** defines the “sort-specific” configuration and supports lateral release of substrates into the IMM.
|
|
GO:0030150
protein import into mitochondrial matrix
|
IMP
PMID:23260140 MITRAC links mitochondrial protein translocation to respirat... |
MARK AS OVER ANNOTATED |
Summary: TIMM21 participates in the TIM23 pathway, but the best-supported human role is TIM23SORT-mediated lateral insertion into the inner membrane rather than matrix-import motor function.
Reason: Prefer TIM23 complex membership and protein insertion into mitochondrial inner membrane for TIMM21; matrix import is primarily a TIM23MOTOR/core translocase output rather than TIMM21-specific activity.
Supporting Evidence:
file:human/TIMM21/TIMM21-deep-research-falcon.md
- **TIM23SORT (lateral insertion/sorting mode):** specialized for **lateral insertion** of single- or dual-pass IMM proteins. In this mode, association with **TIMM21** and **ROMO1** defines the “sort-specific” configuration and supports lateral release of substrates into the IMM.
file:human/TIMM21/TIMM21-deep-research-falcon.md
2) **facilitates lateral insertion** of specific IMM proteins (rather than acting as an enzyme or transporter with a small-molecule substrate).
|
|
GO:0032981
mitochondrial respiratory chain complex I assembly
|
IMP
PMID:23260140 MITRAC links mitochondrial protein translocation to respirat... |
KEEP AS NON CORE |
Summary: Supported as a secondary respiratory-chain assembly linkage, but mitochondrial respiratory chain complex I assembly is not the primary TIMM21 function. The main mechanistic role is TIM23SORT-associated mitochondrial protein insertion/sorting.
Reason: Treat respiratory-chain assembly phenotypes as downstream or context-specific consequences of TIMM21-mediated import/sorting rather than the core molecular role.
Supporting Evidence:
file:human/TIMM21/TIMM21-deep-research-falcon.md
The strongest experimentally grounded respiratory-chain linkage in this evidence set is indirect: TIM23SORT substrates are enriched for OXPHOS/ultrastructure proteins in disease mapping studies, and yeast-centric work links Tim21-containing TIM23 states to respiratory chain interactions (notably complex III) in conserved models.
|
|
GO:0033617
mitochondrial respiratory chain complex IV assembly
|
IMP
PMID:23260140 MITRAC links mitochondrial protein translocation to respirat... |
KEEP AS NON CORE |
Summary: Supported as a secondary respiratory-chain assembly linkage, but mitochondrial respiratory chain complex IV assembly is not the primary TIMM21 function. The main mechanistic role is TIM23SORT-associated mitochondrial protein insertion/sorting.
Reason: Treat respiratory-chain assembly phenotypes as downstream or context-specific consequences of TIMM21-mediated import/sorting rather than the core molecular role.
Supporting Evidence:
file:human/TIMM21/TIMM21-deep-research-falcon.md
The strongest experimentally grounded respiratory-chain linkage in this evidence set is indirect: TIM23SORT substrates are enriched for OXPHOS/ultrastructure proteins in disease mapping studies, and yeast-centric work links Tim21-containing TIM23 states to respiratory chain interactions (notably complex III) in conserved models.
|
|
GO:0003674
molecular_function
|
ND
GO_REF:0000015 |
REMOVE |
Summary: The no-data molecular_function placeholder is superseded by specific evidence for TIMM21 as a TIM23SORT/TIM23 complex accessory factor.
Reason: Specific literature-supported functional annotations are available; the ND molecular_function placeholder should not be retained in a completed review.
Supporting Evidence:
file:human/TIMM21/TIMM21-deep-research-falcon.md
- **TIM23SORT (lateral insertion/sorting mode):** specialized for **lateral insertion** of single- or dual-pass IMM proteins. In this mode, association with **TIMM21** and **ROMO1** defines the “sort-specific” configuration and supports lateral release of substrates into the IMM.
|
|
GO:0045039
protein insertion into mitochondrial inner membrane
|
NAS
file:human/TIMM21/TIMM21-deep-research-falcon.md |
NEW |
Summary: New annotation recommended. TIMM21 is best supported as a TIM23SORT accessory factor that promotes lateral insertion/sorting of selected proteins into the mitochondrial inner membrane.
Reason: Current GOA captures TIM23 complex membership and broad transport terms, but misses the more specific TIM23SORT-associated inner-membrane insertion role.
Supporting Evidence:
file:human/TIMM21/TIMM21-deep-research-falcon.md
- **TIM23SORT (lateral insertion/sorting mode):** specialized for **lateral insertion** of single- or dual-pass IMM proteins. In this mode, association with **TIMM21** and **ROMO1** defines the “sort-specific” configuration and supports lateral release of substrates into the IMM.
file:human/TIMM21/TIMM21-deep-research-falcon.md
2) **facilitates lateral insertion** of specific IMM proteins (rather than acting as an enzyme or transporter with a small-molecule substrate).
|
Q: Which human TIM23SORT client proteins require TIMM21 directly, and which phenotypes attributed to TIMM21 are downstream of altered client insertion?
Q: How much of the reported complex I and complex IV assembly phenotype reflects a direct MITRAC role versus impaired TIM23SORT delivery of OXPHOS assembly substrates?
Experiment: Use TIMM21 knockout/rescue cells with TIMM21 mutants defective for ROMO1/TIM23 association and compare import of matrix-targeted TIM23MOTOR substrates with radiolabeled TIM23SORT inner-membrane substrates by protease protection and BN-PAGE.
Hypothesis: TIMM21 primarily supports TIM23SORT lateral insertion rather than TIM23MOTOR matrix import.
Experiment: Perform quantitative mitochondrial proteomics and pulse import assays after acute TIMM21 depletion, then test whether restoring selected TIM23SORT substrates rescues complex I/IV assembly readouts.
Hypothesis: TIMM21-linked respiratory-chain assembly phenotypes are mediated by defective insertion of a restricted set of OXPHOS assembly clients.
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.
Gene/protein identity and context. The human gene TIMM21 encodes “translocase of inner mitochondrial membrane 21,” a Tim21-family subunit of the mitochondrial TIM23 protein import machinery. TIM23 is the presequence pathway that imports nuclear-encoded proteins bearing N-terminal mitochondrial targeting sequences (presequences) across/into the inner membrane, routing them to the matrix or inner mitochondrial membrane (IMM). TIM23 is broadly responsible for import/sorting of a large fraction of the mitochondrial proteome (commonly cited as ~60%). (zhao2021roleofthe pages 2-3, crameri2024reducedproteinimport pages 1-3)
TIM23 architecture and functional modes. In human cells, TIM23 is organized around a core (TIMM23, TIMM50, TIMM17A/B) and can partition into two functional states:
Operational definition of TIMM21 function. Across human-focused mechanistic literature, TIMM21 is best supported as an accessory TIM23 subunit that:
1) stabilizes/defines TIM23SORT together with ROMO1 and
2) facilitates lateral insertion of specific IMM proteins (rather than acting as an enzyme or transporter with a small-molecule substrate). (reyes2018mutationsintimm50 pages 1-2, crameri2024reducedproteinimport pages 1-3)
TOM–TIM23 “handover” and translocation contact sites (conserved concept). Protein import requires coordination between the outer-membrane TOM complex and inner-membrane TIM23 complex. Reviews of the conserved mechanism describe translocation contact sites where TOM and TIM23 transiently interact during precursor handover. In this framework, Tim21 is discussed as participating in TOM–TIM23 contact-site biology and regulating early transfer steps through the intermembrane space (IMS), though much of this detailed mechanistic evidence is rooted in yeast/conserved systems and then extrapolated to mammals. (horvath2015roleofmembrane pages 4-7, demishteinzohary2017thetim23mitochondrial pages 1-3, chaudhuri2020tim17updatesa pages 10-12)
Quantitative mapping of TIM23SORT substrates and disease sensitivity (2024). A 2024 Molecular and Cellular Biology study of TIMM50-associated mitochondrial disease provides a recent, human-centered quantitative framework for TIM23SORT. From a MitoCarta-derived set of 827 nuclear-encoded IMM/matrix proteins, 711 were annotated as TIM23 substrates, subdivided into 592 predicted TIM23MOTOR substrates and 119 predicted TIM23SORT substrates (with 58 TIM22 substrates). TIM23SORT is explicitly defined by TIMM21 + ROMO1 association, and TIM23SORT substrates were highlighted as particularly sensitive to TIM23 dysfunction in disease contexts. (crameri2024reducedproteinimport pages 9-11)
Human complexome evidence for TIMM21-containing assemblies (2021; still highly informative). Complexome profiling in human cells showed TIMM21 present in high–molecular-mass assemblies and linked its migration to prohibitin/ROMO1-associated scaffolds. TIMM21 (and most of its interaction partners) appeared around ~1,300 kDa, whereas prohibitin and ROMO1 showed broader distributions peaking around ~1,100 kDa. This provides experimentally grounded context for how TIMM21 is organized into larger IMM assemblies rather than acting as a solitary import factor. (guerrero‐castillo2021ablationofmitochondrial pages 11-12, guerrero‐castillo2021ablationofmitochondrial media 7c1a7e84)
Import machinery as a stress signaling hub (2023). Recent reviews emphasize that mitochondrial protein import is not only a “delivery” system but also a regulatory hub that can trigger proteostatic and metabolic responses when impaired. In this expanded view, TIM23 components (including Tim21/TIMM21 in mammalian nomenclature) are discussed as part of a network whose perturbation can elicit cell-wide responses. (chaudhuri2020tim17updatesa pages 10-12)
Patient-derived cybrid rescue experiment (functional implementation). A notable real-world implementation is using TIMM21 modulation to affect mitochondrial disease phenotypes in human cells. In a Nature Communications study focused on TIM23 sorting as a therapeutic target for ATP synthase disorders, lentiviral TIMM21 overexpression in NARP (mtDNA atp6-T8993G) patient-derived cybrids increased survival 2.4-fold (P < 0.05) compared with control, quantified by flow cytometry after 6 days. This supports TIMM21 as a functional lever on TIM23-mediated sorting that can translate to a measurable cellular outcome in disease-relevant models. (aiyar2014mitochondrialproteinsorting pages 3-4, aiyar2014mitochondrialproteinsorting pages 4-5)
Diagnostic/functional genomics workflows implicating TIM23SORT dependencies. In mitochondrial medicine research, TIM23SORT dependencies are now probed using integrated pipelines: patient fibroblast proteomics, BN-PAGE/complexome profiling, and in vitro radiolabeled import assays (often with membrane potential perturbation by FCCP and proteinase K protection) to pinpoint pathway-level defects and sensitive substrate classes. Although this is not TIMM21-specific clinical testing, TIMM21’s role as a defining TIM23SORT component makes it part of the mechanistic interpretation framework. (crameri2024reducedproteinimport pages 9-11, crameri2024reducedproteinimport pages 1-3, crameri2024reducedproteinimport pages 11-12)
Mechanistic consensus (with caveats). Across human-focused mechanistic sources, the most strongly supported annotation for TIMM21 is:
Interpretive caveat on “respiratory chain/complex IV assembly.” Some secondary proteomics/network literature lists TIMM21 among mitochondrial proteins in modules that include respiratory chain factors (including complex IV-associated proteins), but the retrieved evidence set did not provide a definitive, direct mechanistic human study establishing TIMM21 as a dedicated cytochrome c oxidase (complex IV) assembly factor. The strongest experimentally grounded respiratory-chain linkage in this evidence set is indirect: TIM23SORT substrates are enriched for OXPHOS/ultrastructure proteins in disease mapping studies, and yeast-centric work links Tim21-containing TIM23 states to respiratory chain interactions (notably complex III) in conserved models. (crameri2024reducedproteinimport pages 1-3, chaudhuri2020tim17updatesa pages 10-12)
Key quantitative points that directly support functional annotation include:
| Functional/biological role claim | Mechanistic details | Evidence type | Key quantitative/statistical info | Source with URL and year | PaperQA context citation ID(s) |
|---|---|---|---|---|---|
| Human TIMM21 is a TIM23SORT-associated accessory subunit that promotes inner-membrane sorting/lateral insertion | In the human TIM23 pathway, the core complex (TIMM23/TIMM50/TIMM17A/B) partitions into TIM23MOTOR vs TIM23SORT; TIM23SORT is formed by association with TIMM21 and ROMO1 and facilitates lateral insertion of single- or dual-pass membrane proteins into the inner mitochondrial membrane | Primary/recent human-focused study plus human disease mechanistic study | TIM23 pathway imports/sorts a major subset of presequence proteins; Crameri emphasizes TIM23SORT substrate sensitivity in disease | Crameri et al., Molecular and Cellular Biology (2024), https://doi.org/10.1080/10985549.2024.2353652; Reyes et al., EMBO Molecular Medicine (2018), https://doi.org/10.15252/emmm.201708698 | (crameri2024reducedproteinimport pages 1-3, reyes2018mutationsintimm50 pages 1-2) |
| TIMM21 functionally replaces the PAM motor in the sorting mode of TIM23 | TIM23SORT is the form of the translocase used for insertion of MTS-carrying proteins into the IMM; in this mode PAM is replaced by TIMM21, and TIMM21 association with TIM23 is mediated by ROMO1 | Human disease/mechanistic review of primary data | No direct numeric value in excerpt; mechanistic distinction is TIM23SORT vs TIM23MOTOR | Reyes et al., EMBO Molecular Medicine (2018), https://doi.org/10.15252/emmm.201708698 | (reyes2018mutationsintimm50 pages 1-2) |
| Tim21/TIMM21 participates in TOM–TIM23 translocation contact sites | Tim21 is associated with the TIM23 core at early translocation stages and plays a regulatory role in preprotein transfer through the IMS; TOM and TIM23 physically couple transiently during precursor transfer | Review synthesizing primary biochemical studies; mostly yeast/conserved mechanism with relevance to mammalian TIMM21 | Contact sites are transient; no numeric value given in excerpt | Horvath et al., Protein Science (2015), https://doi.org/10.1002/pro.2625 | (horvath2015roleofmembrane pages 4-7) |
| TIM21 contributes to the TIM23–TOM interface through Tim50/Tim21 interactions | TIM23 components participate in initial import from TOM to TIM23; Tim50 interacts with Tom22 and Tim21, supporting a molecular bridge between outer- and inner-membrane translocases | Review; largely conserved mechanism, not direct human-only experiment in excerpt | No numeric value in excerpt | Demishtein-Zohary & Azem, Cell and Tissue Research (2017), https://doi.org/10.1007/s00441-016-2486-7 | (demishteinzohary2017thetim23mitochondrial pages 1-3) |
| TIM21 has a conserved contact-site and respiratory-chain-linked role in non-human model systems | Yeast ScTim21 is an inner-membrane TIM23 subunit with an IMS-exposed region that contacts the TOM trans side and facilitates MOM–MIM contact-site formation; the ScTim21-containing TIM23 complex also interacts with respiratory complex III and assists insertion of sorting-sequence-containing IMM proteins | Review of primary yeast/plant data; inference to human TIMM21 should be cautious | No direct human numeric data; interaction noted with respiratory complex III rather than complex IV | Chaudhuri et al., Biomolecules (2020), https://doi.org/10.3390/biom10121643 | (chaudhuri2020tim17updatesa pages 10-12, chaudhuri2020tim17updatesa pages 2-5) |
| TIMM21 resides in higher-order mitochondrial assemblies linked to TIM23/prohibitin organization | Complexome profiling detected TIMM21 in high-molecular-weight assemblies and suggested partial loading of the prohibitin ring scaffold with TIMM21 and partners; TIMM21-associated assemblies change with mtDNA loss | Primary complexome/proteomics study in human 143B cells | Majority of TIMM21 detected at ~1,300 kDa; prohibitin/ROMO1 peak around ~1,100 kDa | Guerrero-Castillo et al., The EMBO Journal (2021), https://doi.org/10.15252/embj.2021108648 | (guerrero‐castillo2021ablationofmitochondrial pages 11-12) |
| TIM23, the pathway in which TIMM21 operates, is quantitatively central to mitochondrial protein biogenesis | TIM23 is the presequence pathway responsible for matrix import and inner-membrane sorting of many nuclear-encoded mitochondrial proteins | Review | ~60% of the mitochondrial proteome/proteins are imported via the TIM23 complex/pathway | Zhao & Zou, Frontiers in Cardiovascular Medicine (2021), https://doi.org/10.3389/fcvm.2021.749756; Jain et al., Genes (2024), https://doi.org/10.3390/genes15121534 | (zhao2021roleofthe pages 2-3) |
| Direct evidence for human TIMM21 as a complex IV assembly factor is limited in the retrieved evidence | Some secondary/proteomics literature lists TIMM21 among mitochondrial proteins associated with respiratory-chain/complex IV-related modules, but the retrieved targeted evidence did not provide a direct mechanistic human study proving TIMM21 is a bona fide cytochrome c oxidase assembly factor; stronger support exists for TIM23SORT/lateral insertion and respiratory-chain association in yeast | Evidence gap / cautionary interpretation | No robust quantitative human complex IV-specific functional statistic identified in retrieved targeted evidence | Knapp et al., Annals of the New York Academy of Sciences (2019), https://doi.org/10.1111/nyas.14220 | (knapp2019affinityproteomicsidentifies pages 9-11) |
| Disease-association databases currently provide only weak, non-specific signal for TIMM21 | Open Targets returns low-score associations (e.g., vitiligo, spondylolisthesis, acquired thrombocytopenia, sensory perception of smell, hallux rigidus), but these are not TIMM21-specific mechanistic disease annotations and should not be overinterpreted for functional annotation | Database aggregation; exploratory only | Example association scores are low (~0.22–0.24) with evidence count 5 in returned rows | Open Targets platform search for TIMM21 (accessed via tool output), https://platform.opentargets.org/ | (OpenTargets Search: -TIMM21) |
Table: This table condenses the strongest retrieved evidence for human TIMM21/Q9BVV7, emphasizing its role in TIM23SORT-mediated inner-membrane protein sorting, TOM–TIM contact-site biology, and complexome context. It also flags where evidence is indirect or model-organism-derived and where disease associations remain weak or non-specific.
Complexome profiling evidence supporting TIMM21’s assembly into high-molecular-weight TIM23-associated structures (including co-migration with ROMO1/prohibitin-associated assemblies) is shown in a cropped figure region from Guerrero-Castillo et al. (EMBO J 2021) (guerrero‐castillo2021ablationofmitochondrial media 7c1a7e84).
Open Targets currently provides low-score, non-specific associations for TIMM21 (examples returned: vitiligo, spondylolisthesis, acquired thrombocytopenia; scores ~0.22–0.24 with 5 evidence items in returned rows). These should be treated as hypothesis-generating signals rather than mechanistic disease annotation for TIMM21. (OpenTargets Search: -TIMM21)
References
(zhao2021roleofthe pages 2-3): Fujie Zhao and Ming-Hui Zou. Role of the mitochondrial protein import machinery and protein processing in heart disease. Frontiers in Cardiovascular Medicine, Sep 2021. URL: https://doi.org/10.3389/fcvm.2021.749756, doi:10.3389/fcvm.2021.749756. This article has 48 citations and is from a peer-reviewed journal.
(crameri2024reducedproteinimport pages 1-3): Jordan J. Crameri, Catherine S. Palmer, Tegan Stait, Thomas D. Jackson, Matthew Lynch, Adriane Sinclair, Leah E. Frajman, Alison G. Compton, David Coman, David R. Thorburn, Ann E. Frazier, and Diana Stojanovski. Reduced protein import via tim23 sort drives disease pathology in timm50-associated mitochondrial disease. Molecular and Cellular Biology, 44:226-244, Jun 2024. URL: https://doi.org/10.1080/10985549.2024.2353652, doi:10.1080/10985549.2024.2353652. This article has 9 citations and is from a domain leading peer-reviewed journal.
(bogorodskiy2021roleofmitochondrial pages 4-6): Andrey Bogorodskiy, Ivan Okhrimenko, Dmitrii Burkatovskii, Philipp Jakobs, Ivan Maslov, Valentin Gordeliy, Norbert A. Dencher, Thomas Gensch, Wolfgang Voos, Joachim Altschmied, Judith Haendeler, and Valentin Borshchevskiy. Role of mitochondrial protein import in age-related neurodegenerative and cardiovascular diseases. Cells, 10:3528, Dec 2021. URL: https://doi.org/10.3390/cells10123528, doi:10.3390/cells10123528. This article has 25 citations.
(reyes2018mutationsintimm50 pages 1-2): Aurelio Reyes, Laura Melchionda, Alberto Burlina, Alan J Robinson, Daniele Ghezzi, and Massimo Zeviani. Mutations in timm50 compromise cell survival in oxphos‐dependent metabolic conditions. EMBO Molecular Medicine, Sep 2018. URL: https://doi.org/10.15252/emmm.201708698, doi:10.15252/emmm.201708698. This article has 39 citations and is from a highest quality peer-reviewed journal.
(horvath2015roleofmembrane pages 4-7): Susanne E. Horvath, Heike Rampelt, Silke Oeljeklaus, Bettina Warscheid, Martin van der Laan, and Nikolaus Pfanner. Role of membrane contact sites in protein import into mitochondria. Protein Science, 24:277-297, Mar 2015. URL: https://doi.org/10.1002/pro.2625, doi:10.1002/pro.2625. This article has 85 citations and is from a peer-reviewed journal.
(demishteinzohary2017thetim23mitochondrial pages 1-3): Keren Demishtein-Zohary and Abdussalam Azem. The tim23 mitochondrial protein import complex: function and dysfunction. Cell and Tissue Research, 367:33-41, Sep 2017. URL: https://doi.org/10.1007/s00441-016-2486-7, doi:10.1007/s00441-016-2486-7. This article has 59 citations and is from a peer-reviewed journal.
(chaudhuri2020tim17updatesa pages 10-12): Minu Chaudhuri, Chauncey Darden, Fidel Soto Gonzalez, Ujjal K. Singha, Linda Quinones, and Anuj Tripathi. Tim17 updates: a comprehensive review of an ancient mitochondrial protein translocator. Biomolecules, 10:1643, Dec 2020. URL: https://doi.org/10.3390/biom10121643, doi:10.3390/biom10121643. This article has 24 citations.
(crameri2024reducedproteinimport pages 9-11): Jordan J. Crameri, Catherine S. Palmer, Tegan Stait, Thomas D. Jackson, Matthew Lynch, Adriane Sinclair, Leah E. Frajman, Alison G. Compton, David Coman, David R. Thorburn, Ann E. Frazier, and Diana Stojanovski. Reduced protein import via tim23 sort drives disease pathology in timm50-associated mitochondrial disease. Molecular and Cellular Biology, 44:226-244, Jun 2024. URL: https://doi.org/10.1080/10985549.2024.2353652, doi:10.1080/10985549.2024.2353652. This article has 9 citations and is from a domain leading peer-reviewed journal.
(guerrero‐castillo2021ablationofmitochondrial pages 11-12): Sergio Guerrero‐Castillo, Joeri van Strien, Ulrich Brandt, and Susanne Arnold. Ablation of mitochondrial dna results in widespread remodeling of the mitochondrial complexome. The EMBO Journal, Sep 2021. URL: https://doi.org/10.15252/embj.2021108648, doi:10.15252/embj.2021108648. This article has 36 citations.
(guerrero‐castillo2021ablationofmitochondrial media 7c1a7e84): Sergio Guerrero‐Castillo, Joeri van Strien, Ulrich Brandt, and Susanne Arnold. Ablation of mitochondrial dna results in widespread remodeling of the mitochondrial complexome. The EMBO Journal, Sep 2021. URL: https://doi.org/10.15252/embj.2021108648, doi:10.15252/embj.2021108648. This article has 36 citations.
(aiyar2014mitochondrialproteinsorting pages 3-4): Raeka S. Aiyar, Maria Bohnert, Stéphane Duvezin-Caubet, Cécile Voisset, Julien Gagneur, Emilie S. Fritsch, Elodie Couplan, Karina von der Malsburg, Charlotta Funaya, Flavie Soubigou, Florence Courtin, Sundari Suresh, Roza Kucharczyk, Justine Evrard, Claude Antony, Robert P. St.Onge, Marc Blondel, Jean-Paul di Rago, Martin van der Laan, and Lars M. Steinmetz. Mitochondrial protein sorting as a therapeutic target for atp synthase disorders. Nature Communications, Dec 2014. URL: https://doi.org/10.1038/ncomms6585, doi:10.1038/ncomms6585. This article has 41 citations and is from a highest quality peer-reviewed journal.
(aiyar2014mitochondrialproteinsorting pages 4-5): Raeka S. Aiyar, Maria Bohnert, Stéphane Duvezin-Caubet, Cécile Voisset, Julien Gagneur, Emilie S. Fritsch, Elodie Couplan, Karina von der Malsburg, Charlotta Funaya, Flavie Soubigou, Florence Courtin, Sundari Suresh, Roza Kucharczyk, Justine Evrard, Claude Antony, Robert P. St.Onge, Marc Blondel, Jean-Paul di Rago, Martin van der Laan, and Lars M. Steinmetz. Mitochondrial protein sorting as a therapeutic target for atp synthase disorders. Nature Communications, Dec 2014. URL: https://doi.org/10.1038/ncomms6585, doi:10.1038/ncomms6585. This article has 41 citations and is from a highest quality peer-reviewed journal.
(crameri2024reducedproteinimport pages 11-12): Jordan J. Crameri, Catherine S. Palmer, Tegan Stait, Thomas D. Jackson, Matthew Lynch, Adriane Sinclair, Leah E. Frajman, Alison G. Compton, David Coman, David R. Thorburn, Ann E. Frazier, and Diana Stojanovski. Reduced protein import via tim23 sort drives disease pathology in timm50-associated mitochondrial disease. Molecular and Cellular Biology, 44:226-244, Jun 2024. URL: https://doi.org/10.1080/10985549.2024.2353652, doi:10.1080/10985549.2024.2353652. This article has 9 citations and is from a domain leading peer-reviewed journal.
(chaudhuri2020tim17updatesa pages 2-5): Minu Chaudhuri, Chauncey Darden, Fidel Soto Gonzalez, Ujjal K. Singha, Linda Quinones, and Anuj Tripathi. Tim17 updates: a comprehensive review of an ancient mitochondrial protein translocator. Biomolecules, 10:1643, Dec 2020. URL: https://doi.org/10.3390/biom10121643, doi:10.3390/biom10121643. This article has 24 citations.
(knapp2019affinityproteomicsidentifies pages 9-11): Barbara Knapp, Jens Roedig, Karsten Boldt, Jacek Krzysko, Nicola Horn, Marius Ueffing, and Uwe Wolfrum. Affinity proteomics identifies novel functional modules related to adhesion gpcrs. Annals of the New York Academy of Sciences, 1456:144-167, Nov 2019. URL: https://doi.org/10.1111/nyas.14220, doi:10.1111/nyas.14220. This article has 28 citations and is from a peer-reviewed journal.
(OpenTargets Search: -TIMM21): Open Targets Query (-TIMM21, 5 results). Buniello, A. et al. (2025). Open Targets Platform: facilitating therapeutic hypotheses building in drug discovery. Nucleic Acids Research.
id: Q9BVV7
gene_symbol: TIMM21
product_type: PROTEIN
status: COMPLETE
taxon:
id: NCBITaxon:9606
label: Homo sapiens
description: TIMM21 encodes a non-enzymatic accessory subunit of the mitochondrial TIM23 presequence translocase. In human cells it is best supported as a TIM23SORT factor that works with ROMO1 to promote lateral insertion/sorting of selected presequence-containing proteins into the inner mitochondrial membrane, with secondary links to respiratory-chain assembly contexts through this import/sorting role.
existing_annotations:
- term:
id: GO:0005744
label: TIM23 mitochondrial import inner membrane translocase complex
evidence_type: IBA
original_reference_id: GO_REF:0000033
review:
summary: Correct. TIMM21 is a TIM23-associated accessory subunit and, with ROMO1, defines the TIM23SORT state of the TIM23 presequence translocase.
action: ACCEPT
additional_reference_ids:
- file:human/TIMM21/TIMM21-deep-research-falcon.md
supported_by:
- reference_id: file:human/TIMM21/TIMM21-deep-research-falcon.md
supporting_text: '- **TIM23SORT (lateral insertion/sorting mode):** specialized for **lateral insertion** of single- or dual-pass IMM proteins. In this mode, association with **TIMM21** and **ROMO1** defines the “sort-specific” configuration and supports lateral release of substrates into the IMM.'
- term:
id: GO:0030150
label: protein import into mitochondrial matrix
evidence_type: IBA
original_reference_id: GO_REF:0000033
review:
summary: TIMM21 participates in the TIM23 pathway, but the best-supported human role is TIM23SORT-mediated lateral insertion into the inner membrane rather than matrix-import motor function.
action: MARK_AS_OVER_ANNOTATED
additional_reference_ids:
- file:human/TIMM21/TIMM21-deep-research-falcon.md
reason: Prefer TIM23 complex membership and protein insertion into mitochondrial inner membrane for TIMM21; matrix import is primarily a TIM23MOTOR/core translocase output rather than TIMM21-specific activity.
supported_by:
- reference_id: file:human/TIMM21/TIMM21-deep-research-falcon.md
supporting_text: '- **TIM23SORT (lateral insertion/sorting mode):** specialized for **lateral insertion** of single- or dual-pass IMM proteins. In this mode, association with **TIMM21** and **ROMO1** defines the “sort-specific” configuration and supports lateral release of substrates into the IMM.'
- reference_id: file:human/TIMM21/TIMM21-deep-research-falcon.md
supporting_text: 2) **facilitates lateral insertion** of specific IMM proteins (rather than acting as an enzyme or transporter with a small-molecule substrate).
- term:
id: GO:0005744
label: TIM23 mitochondrial import inner membrane translocase complex
evidence_type: IEA
original_reference_id: GO_REF:0000002
review:
summary: Correct. TIMM21 is a TIM23-associated accessory subunit and, with ROMO1, defines the TIM23SORT state of the TIM23 presequence translocase.
action: ACCEPT
additional_reference_ids:
- file:human/TIMM21/TIMM21-deep-research-falcon.md
supported_by:
- reference_id: file:human/TIMM21/TIMM21-deep-research-falcon.md
supporting_text: '- **TIM23SORT (lateral insertion/sorting mode):** specialized for **lateral insertion** of single- or dual-pass IMM proteins. In this mode, association with **TIMM21** and **ROMO1** defines the “sort-specific” configuration and supports lateral release of substrates into the IMM.'
- term:
id: GO:0030150
label: protein import into mitochondrial matrix
evidence_type: IEA
original_reference_id: GO_REF:0000002
review:
summary: TIMM21 participates in the TIM23 pathway, but the best-supported human role is TIM23SORT-mediated lateral insertion into the inner membrane rather than matrix-import motor function.
action: MARK_AS_OVER_ANNOTATED
additional_reference_ids:
- file:human/TIMM21/TIMM21-deep-research-falcon.md
reason: Prefer TIM23 complex membership and protein insertion into mitochondrial inner membrane for TIMM21; matrix import is primarily a TIM23MOTOR/core translocase output rather than TIMM21-specific activity.
supported_by:
- reference_id: file:human/TIMM21/TIMM21-deep-research-falcon.md
supporting_text: '- **TIM23SORT (lateral insertion/sorting mode):** specialized for **lateral insertion** of single- or dual-pass IMM proteins. In this mode, association with **TIMM21** and **ROMO1** defines the “sort-specific” configuration and supports lateral release of substrates into the IMM.'
- reference_id: file:human/TIMM21/TIMM21-deep-research-falcon.md
supporting_text: 2) **facilitates lateral insertion** of specific IMM proteins (rather than acting as an enzyme or transporter with a small-molecule substrate).
- term:
id: GO:0031966
label: mitochondrial membrane
evidence_type: IEA
original_reference_id: GO_REF:0000044
review:
summary: Correct but too broad. TIMM21 is specifically associated with the mitochondrial inner membrane TIM23 machinery.
action: MARK_AS_OVER_ANNOTATED
additional_reference_ids:
- file:human/TIMM21/TIMM21-deep-research-falcon.md
reason: Use mitochondrial inner membrane and TIM23 complex annotations instead of generic mitochondrial membrane.
supported_by:
- reference_id: file:human/TIMM21/TIMM21-deep-research-falcon.md
supporting_text: '- **Cellular location:** mitochondria, associated with the **inner mitochondrial membrane** as part of TIM23-related assemblies. (crameri2024reducedproteinimport pages 1-3)'
- term:
id: GO:0005515
label: protein binding
evidence_type: IPI
original_reference_id: PMID:23260140
review:
summary: Protein binding is too generic for TIMM21. The informative biology is TIM23SORT/TIM23-complex association with ROMO1/TIM23 machinery rather than undifferentiated binding.
action: MARK_AS_OVER_ANNOTATED
additional_reference_ids:
- file:human/TIMM21/TIMM21-deep-research-falcon.md
reason: Replace generic protein binding interpretation with specific TIM23 complex and TIM23SORT functional context.
supported_by:
- reference_id: file:human/TIMM21/TIMM21-deep-research-falcon.md
supporting_text: '- **TIM23SORT (lateral insertion/sorting mode):** specialized for **lateral insertion** of single- or dual-pass IMM proteins. In this mode, association with **TIMM21** and **ROMO1** defines the “sort-specific” configuration and supports lateral release of substrates into the IMM.'
- term:
id: GO:0005515
label: protein binding
evidence_type: IPI
original_reference_id: PMID:32296183
review:
summary: Protein binding is too generic for TIMM21. The informative biology is TIM23SORT/TIM23-complex association with ROMO1/TIM23 machinery rather than undifferentiated binding.
action: MARK_AS_OVER_ANNOTATED
additional_reference_ids:
- file:human/TIMM21/TIMM21-deep-research-falcon.md
reason: Replace generic protein binding interpretation with specific TIM23 complex and TIM23SORT functional context.
supported_by:
- reference_id: file:human/TIMM21/TIMM21-deep-research-falcon.md
supporting_text: '- **TIM23SORT (lateral insertion/sorting mode):** specialized for **lateral insertion** of single- or dual-pass IMM proteins. In this mode, association with **TIMM21** and **ROMO1** defines the “sort-specific” configuration and supports lateral release of substrates into the IMM.'
- term:
id: GO:0005743
label: mitochondrial inner membrane
evidence_type: NAS
original_reference_id: PMID:10339406
review:
summary: Correct. TIMM21 is associated with the mitochondrial inner membrane as part of TIM23-related assemblies.
action: ACCEPT
additional_reference_ids:
- file:human/TIMM21/TIMM21-deep-research-falcon.md
supported_by:
- reference_id: file:human/TIMM21/TIMM21-deep-research-falcon.md
supporting_text: '- **Cellular location:** mitochondria, associated with the **inner mitochondrial membrane** as part of TIM23-related assemblies. (crameri2024reducedproteinimport pages 1-3)'
- term:
id: GO:0005744
label: TIM23 mitochondrial import inner membrane translocase complex
evidence_type: NAS
original_reference_id: PMID:10339406
review:
summary: Correct. TIMM21 is a TIM23-associated accessory subunit and, with ROMO1, defines the TIM23SORT state of the TIM23 presequence translocase.
action: ACCEPT
additional_reference_ids:
- file:human/TIMM21/TIMM21-deep-research-falcon.md
supported_by:
- reference_id: file:human/TIMM21/TIMM21-deep-research-falcon.md
supporting_text: '- **TIM23SORT (lateral insertion/sorting mode):** specialized for **lateral insertion** of single- or dual-pass IMM proteins. In this mode, association with **TIMM21** and **ROMO1** defines the “sort-specific” configuration and supports lateral release of substrates into the IMM.'
- term:
id: GO:0006886
label: intracellular protein transport
evidence_type: NAS
original_reference_id: PMID:10339406
review:
summary: Correct pathway family but too broad. TIMM21 is specifically involved in TIM23SORT-mediated mitochondrial inner-membrane protein insertion/sorting.
action: MARK_AS_OVER_ANNOTATED
additional_reference_ids:
- file:human/TIMM21/TIMM21-deep-research-falcon.md
reason: Use specific mitochondrial protein import/sorting terms and TIM23 complex annotation rather than generic intracellular protein transport.
supported_by:
- reference_id: file:human/TIMM21/TIMM21-deep-research-falcon.md
supporting_text: '- **TIM23SORT (lateral insertion/sorting mode):** specialized for **lateral insertion** of single- or dual-pass IMM proteins. In this mode, association with **TIMM21** and **ROMO1** defines the “sort-specific” configuration and supports lateral release of substrates into the IMM.'
- reference_id: file:human/TIMM21/TIMM21-deep-research-falcon.md
supporting_text: 2) **facilitates lateral insertion** of specific IMM proteins (rather than acting as an enzyme or transporter with a small-molecule substrate).
- term:
id: GO:0005739
label: mitochondrion
evidence_type: HTP
original_reference_id: PMID:34800366
review:
summary: Correct but broad. TIMM21 is better captured by mitochondrial inner membrane and TIM23 complex annotations.
action: MARK_AS_OVER_ANNOTATED
additional_reference_ids:
- file:human/TIMM21/TIMM21-deep-research-falcon.md
reason: Prefer mitochondrial inner membrane/TIM23 complex over generic mitochondrion.
supported_by:
- reference_id: file:human/TIMM21/TIMM21-deep-research-falcon.md
supporting_text: '- **Cellular location:** mitochondria, associated with the **inner mitochondrial membrane** as part of TIM23-related assemblies. (crameri2024reducedproteinimport pages 1-3)'
- term:
id: GO:0005758
label: mitochondrial intermembrane space
evidence_type: TAS
original_reference_id: Reactome:R-HSA-9865412
review:
summary: Supported as TIMM21 function at the inner-membrane/intermembrane-space interface during TOM-TIM23 handover, not as a soluble IMS protein.
action: ACCEPT
additional_reference_ids:
- file:human/TIMM21/TIMM21-deep-research-falcon.md
supported_by:
- reference_id: file:human/TIMM21/TIMM21-deep-research-falcon.md
supporting_text: In this framework, **Tim21** is discussed as participating in TOM–TIM23 contact-site biology and regulating early transfer steps through the intermembrane space (IMS), though much of this detailed mechanistic evidence is rooted in yeast/conserved systems and then extrapolated to mammals.
- term:
id: GO:0005758
label: mitochondrial intermembrane space
evidence_type: TAS
original_reference_id: Reactome:R-HSA-9865579
review:
summary: Supported as TIMM21 function at the inner-membrane/intermembrane-space interface during TOM-TIM23 handover, not as a soluble IMS protein.
action: ACCEPT
additional_reference_ids:
- file:human/TIMM21/TIMM21-deep-research-falcon.md
supported_by:
- reference_id: file:human/TIMM21/TIMM21-deep-research-falcon.md
supporting_text: In this framework, **Tim21** is discussed as participating in TOM–TIM23 contact-site biology and regulating early transfer steps through the intermembrane space (IMS), though much of this detailed mechanistic evidence is rooted in yeast/conserved systems and then extrapolated to mammals.
- term:
id: GO:0005744
label: TIM23 mitochondrial import inner membrane translocase complex
evidence_type: IDA
original_reference_id: PMID:30598479
review:
summary: Correct. TIMM21 is a TIM23-associated accessory subunit and, with ROMO1, defines the TIM23SORT state of the TIM23 presequence translocase.
action: ACCEPT
additional_reference_ids:
- file:human/TIMM21/TIMM21-deep-research-falcon.md
supported_by:
- reference_id: file:human/TIMM21/TIMM21-deep-research-falcon.md
supporting_text: '- **TIM23SORT (lateral insertion/sorting mode):** specialized for **lateral insertion** of single- or dual-pass IMM proteins. In this mode, association with **TIMM21** and **ROMO1** defines the “sort-specific” configuration and supports lateral release of substrates into the IMM.'
- term:
id: GO:0005515
label: protein binding
evidence_type: IPI
original_reference_id: PMID:26321642
review:
summary: Protein binding is too generic for TIMM21. The informative biology is TIM23SORT/TIM23-complex association with ROMO1/TIM23 machinery rather than undifferentiated binding.
action: MARK_AS_OVER_ANNOTATED
additional_reference_ids:
- file:human/TIMM21/TIMM21-deep-research-falcon.md
reason: Replace generic protein binding interpretation with specific TIM23 complex and TIM23SORT functional context.
supported_by:
- reference_id: file:human/TIMM21/TIMM21-deep-research-falcon.md
supporting_text: '- **TIM23SORT (lateral insertion/sorting mode):** specialized for **lateral insertion** of single- or dual-pass IMM proteins. In this mode, association with **TIMM21** and **ROMO1** defines the “sort-specific” configuration and supports lateral release of substrates into the IMM.'
- term:
id: GO:0005743
label: mitochondrial inner membrane
evidence_type: TAS
original_reference_id: Reactome:R-HSA-9865412
review:
summary: Correct. TIMM21 is associated with the mitochondrial inner membrane as part of TIM23-related assemblies.
action: ACCEPT
additional_reference_ids:
- file:human/TIMM21/TIMM21-deep-research-falcon.md
supported_by:
- reference_id: file:human/TIMM21/TIMM21-deep-research-falcon.md
supporting_text: '- **Cellular location:** mitochondria, associated with the **inner mitochondrial membrane** as part of TIM23-related assemblies. (crameri2024reducedproteinimport pages 1-3)'
- term:
id: GO:0005743
label: mitochondrial inner membrane
evidence_type: TAS
original_reference_id: Reactome:R-HSA-9865449
review:
summary: Correct. TIMM21 is associated with the mitochondrial inner membrane as part of TIM23-related assemblies.
action: ACCEPT
additional_reference_ids:
- file:human/TIMM21/TIMM21-deep-research-falcon.md
supported_by:
- reference_id: file:human/TIMM21/TIMM21-deep-research-falcon.md
supporting_text: '- **Cellular location:** mitochondria, associated with the **inner mitochondrial membrane** as part of TIM23-related assemblies. (crameri2024reducedproteinimport pages 1-3)'
- term:
id: GO:0005743
label: mitochondrial inner membrane
evidence_type: TAS
original_reference_id: Reactome:R-HSA-9865579
review:
summary: Correct. TIMM21 is associated with the mitochondrial inner membrane as part of TIM23-related assemblies.
action: ACCEPT
additional_reference_ids:
- file:human/TIMM21/TIMM21-deep-research-falcon.md
supported_by:
- reference_id: file:human/TIMM21/TIMM21-deep-research-falcon.md
supporting_text: '- **Cellular location:** mitochondria, associated with the **inner mitochondrial membrane** as part of TIM23-related assemblies. (crameri2024reducedproteinimport pages 1-3)'
- term:
id: GO:0005744
label: TIM23 mitochondrial import inner membrane translocase complex
evidence_type: IDA
original_reference_id: PMID:23260140
review:
summary: Correct. TIMM21 is a TIM23-associated accessory subunit and, with ROMO1, defines the TIM23SORT state of the TIM23 presequence translocase.
action: ACCEPT
additional_reference_ids:
- file:human/TIMM21/TIMM21-deep-research-falcon.md
supported_by:
- reference_id: file:human/TIMM21/TIMM21-deep-research-falcon.md
supporting_text: '- **TIM23SORT (lateral insertion/sorting mode):** specialized for **lateral insertion** of single- or dual-pass IMM proteins. In this mode, association with **TIMM21** and **ROMO1** defines the “sort-specific” configuration and supports lateral release of substrates into the IMM.'
- term:
id: GO:0030150
label: protein import into mitochondrial matrix
evidence_type: IMP
original_reference_id: PMID:23260140
review:
summary: TIMM21 participates in the TIM23 pathway, but the best-supported human role is TIM23SORT-mediated lateral insertion into the inner membrane rather than matrix-import motor function.
action: MARK_AS_OVER_ANNOTATED
additional_reference_ids:
- file:human/TIMM21/TIMM21-deep-research-falcon.md
reason: Prefer TIM23 complex membership and protein insertion into mitochondrial inner membrane for TIMM21; matrix import is primarily a TIM23MOTOR/core translocase output rather than TIMM21-specific activity.
supported_by:
- reference_id: file:human/TIMM21/TIMM21-deep-research-falcon.md
supporting_text: '- **TIM23SORT (lateral insertion/sorting mode):** specialized for **lateral insertion** of single- or dual-pass IMM proteins. In this mode, association with **TIMM21** and **ROMO1** defines the “sort-specific” configuration and supports lateral release of substrates into the IMM.'
- reference_id: file:human/TIMM21/TIMM21-deep-research-falcon.md
supporting_text: 2) **facilitates lateral insertion** of specific IMM proteins (rather than acting as an enzyme or transporter with a small-molecule substrate).
- term:
id: GO:0032981
label: mitochondrial respiratory chain complex I assembly
evidence_type: IMP
original_reference_id: PMID:23260140
review:
summary: Supported as a secondary respiratory-chain assembly linkage, but mitochondrial respiratory chain complex I assembly is not the primary TIMM21 function. The main mechanistic role is TIM23SORT-associated mitochondrial protein insertion/sorting.
action: KEEP_AS_NON_CORE
additional_reference_ids:
- file:human/TIMM21/TIMM21-deep-research-falcon.md
reason: Treat respiratory-chain assembly phenotypes as downstream or context-specific consequences of TIMM21-mediated import/sorting rather than the core molecular role.
supported_by:
- reference_id: file:human/TIMM21/TIMM21-deep-research-falcon.md
supporting_text: 'The strongest experimentally grounded respiratory-chain linkage in this evidence set is indirect: TIM23SORT substrates are enriched for OXPHOS/ultrastructure proteins in disease mapping studies, and yeast-centric work links Tim21-containing TIM23 states to respiratory chain interactions (notably complex III) in conserved models.'
- term:
id: GO:0033617
label: mitochondrial respiratory chain complex IV assembly
evidence_type: IMP
original_reference_id: PMID:23260140
review:
summary: Supported as a secondary respiratory-chain assembly linkage, but mitochondrial respiratory chain complex IV assembly is not the primary TIMM21 function. The main mechanistic role is TIM23SORT-associated mitochondrial protein insertion/sorting.
action: KEEP_AS_NON_CORE
additional_reference_ids:
- file:human/TIMM21/TIMM21-deep-research-falcon.md
reason: Treat respiratory-chain assembly phenotypes as downstream or context-specific consequences of TIMM21-mediated import/sorting rather than the core molecular role.
supported_by:
- reference_id: file:human/TIMM21/TIMM21-deep-research-falcon.md
supporting_text: 'The strongest experimentally grounded respiratory-chain linkage in this evidence set is indirect: TIM23SORT substrates are enriched for OXPHOS/ultrastructure proteins in disease mapping studies, and yeast-centric work links Tim21-containing TIM23 states to respiratory chain interactions (notably complex III) in conserved models.'
- term:
id: GO:0003674
label: molecular_function
evidence_type: ND
original_reference_id: GO_REF:0000015
review:
summary: The no-data molecular_function placeholder is superseded by specific evidence for TIMM21 as a TIM23SORT/TIM23 complex accessory factor.
action: REMOVE
additional_reference_ids:
- file:human/TIMM21/TIMM21-deep-research-falcon.md
reason: Specific literature-supported functional annotations are available; the ND molecular_function placeholder should not be retained in a completed review.
supported_by:
- reference_id: file:human/TIMM21/TIMM21-deep-research-falcon.md
supporting_text: '- **TIM23SORT (lateral insertion/sorting mode):** specialized for **lateral insertion** of single- or dual-pass IMM proteins. In this mode, association with **TIMM21** and **ROMO1** defines the “sort-specific” configuration and supports lateral release of substrates into the IMM.'
- term:
id: GO:0045039
label: protein insertion into mitochondrial inner membrane
evidence_type: NAS
original_reference_id: file:human/TIMM21/TIMM21-deep-research-falcon.md
review:
summary: New annotation recommended. TIMM21 is best supported as a TIM23SORT accessory factor that promotes lateral insertion/sorting of selected proteins into the mitochondrial inner membrane.
action: NEW
additional_reference_ids:
- file:human/TIMM21/TIMM21-deep-research-falcon.md
reason: Current GOA captures TIM23 complex membership and broad transport terms, but misses the more specific TIM23SORT-associated inner-membrane insertion role.
supported_by:
- reference_id: file:human/TIMM21/TIMM21-deep-research-falcon.md
supporting_text: '- **TIM23SORT (lateral insertion/sorting mode):** specialized for **lateral insertion** of single- or dual-pass IMM proteins. In this mode, association with **TIMM21** and **ROMO1** defines the “sort-specific” configuration and supports lateral release of substrates into the IMM.'
- reference_id: file:human/TIMM21/TIMM21-deep-research-falcon.md
supporting_text: 2) **facilitates lateral insertion** of specific IMM proteins (rather than acting as an enzyme or transporter with a small-molecule substrate).
references:
- id: GO_REF:0000002
title: Gene Ontology annotation through association of InterPro records with GO terms
findings: []
- id: GO_REF:0000015
title: Use of the ND evidence code for Gene Ontology (GO) terms
findings: []
- id: GO_REF:0000033
title: Annotation inferences using phylogenetic trees
findings: []
- id: GO_REF:0000044
title: Gene Ontology annotation based on UniProtKB/Swiss-Prot Subcellular Location vocabulary mapping, accompanied by conservative changes to GO terms applied by UniProt
findings: []
- id: PMID:10339406
title: Genetic and structural characterization of the human mitochondrial inner membrane translocase.
findings: []
- id: PMID:23260140
title: MITRAC links mitochondrial protein translocation to respiratory-chain assembly and translational regulation.
findings: []
- id: PMID:26321642
title: MITRAC7 Acts as a COX1-Specific Chaperone and Reveals a Checkpoint during Cytochrome c Oxidase Assembly.
findings: []
- id: PMID:30598479
title: ROMO1 is a constituent of the human presequence translocase required for YME1L protease import.
findings: []
- id: PMID:32296183
title: A reference map of the human binary protein interactome.
findings: []
- id: PMID:34800366
title: Quantitative high-confidence human mitochondrial proteome and its dynamics in cellular context.
findings: []
- id: Reactome:R-HSA-9865412
title: TIMM21 carries COX4, COX5A, COX6C to MT-CO1:MITRAC
findings: []
- id: Reactome:R-HSA-9865449
title: Metallochaperone inserts Cu2+ into MT-CO1
findings: []
- id: Reactome:R-HSA-9865579
title: MT-CO1 and MT-CO2 complexes associate, installing heme moieties
findings: []
- id: file:human/TIMM21/TIMM21-deep-research-falcon.md
title: Falcon deep research report for human TIMM21
findings: []
core_functions:
- description: TIMM21 is a non-enzymatic accessory subunit of the mitochondrial TIM23 presequence translocase that, together with ROMO1, defines the TIM23SORT state and supports lateral insertion/sorting of selected presequence-containing proteins into the inner mitochondrial membrane.
supported_by:
- reference_id: file:human/TIMM21/TIMM21-deep-research-falcon.md
supporting_text: '- **TIM23SORT (lateral insertion/sorting mode):** specialized for **lateral insertion** of single- or dual-pass IMM proteins. In this mode, association with **TIMM21** and **ROMO1** defines the “sort-specific” configuration and supports lateral release of substrates into the IMM.'
- reference_id: file:human/TIMM21/TIMM21-deep-research-falcon.md
supporting_text: 2) **facilitates lateral insertion** of specific IMM proteins (rather than acting as an enzyme or transporter with a small-molecule substrate).
- reference_id: file:human/TIMM21/TIMM21-deep-research-falcon.md
supporting_text: '- **Cellular location:** mitochondria, associated with the **inner mitochondrial membrane** as part of TIM23-related assemblies. (crameri2024reducedproteinimport pages 1-3)'
directly_involved_in:
- id: GO:0045039
label: protein insertion into mitochondrial inner membrane
locations:
- id: GO:0005743
label: mitochondrial inner membrane
- id: GO:0005758
label: mitochondrial intermembrane space
in_complex:
id: GO:0005744
label: TIM23 mitochondrial import inner membrane translocase complex
proposed_new_terms: []
suggested_questions:
- question: Which human TIM23SORT client proteins require TIMM21 directly, and which phenotypes attributed to TIMM21 are downstream of altered client insertion?
experts: []
- question: How much of the reported complex I and complex IV assembly phenotype reflects a direct MITRAC role versus impaired TIM23SORT delivery of OXPHOS assembly substrates?
experts: []
suggested_experiments:
- hypothesis: TIMM21 primarily supports TIM23SORT lateral insertion rather than TIM23MOTOR matrix import.
description: Use TIMM21 knockout/rescue cells with TIMM21 mutants defective for ROMO1/TIM23 association and compare import of matrix-targeted TIM23MOTOR substrates with radiolabeled TIM23SORT inner-membrane substrates by protease protection and BN-PAGE.
- hypothesis: TIMM21-linked respiratory-chain assembly phenotypes are mediated by defective insertion of a restricted set of OXPHOS assembly clients.
description: Perform quantitative mitochondrial proteomics and pulse import assays after acute TIMM21 depletion, then test whether restoring selected TIM23SORT substrates rescues complex I/IV assembly readouts.