TMEM70 is a scaffold protein of the inner mitochondrial membrane that plays a critical role in the biogenesis of mitochondrial ATP synthase (Complex V). It facilitates the membrane insertion and oligomer formation of the subunit c (ATP5MC1) into the c8-ring, which is the membrane sector of the enzyme's rotor. TMEM70 forms oligomeric scaffolds within mitochondrial cristae that promote in situ assembly of the ATP synthase proton channel. TMEM70 deficiency causes severe ATP synthase deficiency and neonatal mitochondrial encephalocardiomyopathy. TMEM70 also has a secondary role in the stability of Complex I membrane-bound subassemblies through interaction with the MCIA complex.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0031966 mitochondrial membrane | IBA GO_REF:0000033 | ACCEPT | Summary: TMEM70 is confirmed to localize to the mitochondrial inner membrane based on multiple experimental studies. While this IBA annotation is correct, it is less specific than what is experimentally demonstrated - TMEM70 localizes specifically to the inner mitochondrial membrane and cristae. Reason: This annotation is phylogenetically inferred and is broadly correct. Multiple experimental studies confirm mitochondrial membrane localization. UniProt states TMEM70 is located in "Mitochondrion inner membrane; Multi-pass membrane protein" (PMID:20937241, PMID:24576557, PMID:33359711). While a more specific term (GO:0005743 mitochondrial inner membrane) would be preferable, this annotation is valid as a broader term. Supporting Evidence: PMID:24576557 We used tagged forms of TMEM70 and demonstrated that it has a hairpin structure with the N- and C-termini oriented towards the mitochondrial matrix. file:human/TMEM70/TMEM70-deep-research-falcon.md model: Edison Scientific Literature |
| GO:0033615 mitochondrial proton-transporting ATP synthase complex assembly | IBA GO_REF:0000033 | ACCEPT | Summary: This IBA annotation correctly captures the core biological function of TMEM70. The protein is a scaffold factor essential for ATP synthase (Complex V) assembly, specifically required for the formation of the c8-ring component of the enzyme's rotor. Reason: This is the core function of TMEM70. Multiple experimental studies demonstrate that TMEM70 functions in ATP synthase biogenesis by promoting subunit c incorporation into the c8-ring. Loss of TMEM70 results in severe ATP synthase deficiency with accumulation of the F1 sector and loss of the Fo proton channel (PMID:18953340, PMID:31652072, PMID:32275929, PMID:33359711, PMID:33753518). Supporting Evidence: PMID:31652072 Altogether, we identified TMEM70 as specific ancillary factor for subunit c PMID:33753518 One such module is the c8-ring, which provides the membrane sector of the enzyme's rotor, and its assembly is influenced by another transmembrane (TMEM) protein, TMEM70. |
| GO:0005743 mitochondrial inner membrane | IEA GO_REF:0000044 | ACCEPT | Summary: This IEA annotation based on UniProt subcellular location mapping is correct. TMEM70 is a transmembrane protein of the mitochondrial inner membrane with two transmembrane helices and both termini facing the matrix. Reason: TMEM70 is confirmed to be an integral inner mitochondrial membrane protein by multiple experimental studies. UniProt annotation is based on experimental evidence from PMID:20937241, PMID:24576557, and PMID:33359711. This is more specific than the IBA annotation for mitochondrial membrane and accurately represents the localization. Supporting Evidence: PMID:24576557 We used tagged forms of TMEM70 and demonstrated that it has a hairpin structure with the N- and C-termini oriented towards the mitochondrial matrix. |
| GO:0005515 protein binding | IPI PMID:32296183 A reference map of the human binary protein interactome. | REMOVE | Summary: This annotation is based on a large-scale binary protein interactome study. While TMEM70 does interact with proteins, the generic GO:0005515 protein binding term is uninformative and does not capture the specific functional interactions of TMEM70. Reason: GO:0005515 protein binding is too vague and uninformative. TMEM70 has specific functional interactions with ATP synthase subunit c (ATP5MC1), TMEM242, and MCIA complex components (ACAD9, ECSIT, NDUFAF1, TMEM126B, TIMMDC1) that are captured by more informative terms like GO:0140260 (mitochondrial proton-transporting ATP synthase complex binding). The reference PMID:32296183 is a high-throughput interactome study that does not provide functional context for TMEM70 specifically. Supporting Evidence: PMID:32296183 Apr 8. A reference map of the human binary protein interactome. |
| GO:0005739 mitochondrion | IDA GO_REF:0000052 | ACCEPT | Summary: This IDA annotation based on HPA immunofluorescence curation is correct but less specific than what is known. TMEM70 is specifically localized to the mitochondrial inner membrane. Reason: TMEM70 mitochondrial localization is well-established. While this annotation is less specific than GO:0005743 (mitochondrial inner membrane), it is correct. The GO_REF:0000052 reference indicates curation of immunofluorescence data by HPA, which is appropriate for this general localization term. |
| GO:0005743 mitochondrial inner membrane | IDA PMID:32275929 TMEM70 functions in the assembly of complexes I and V. | ACCEPT | Summary: This IDA annotation correctly identifies TMEM70 localization at the mitochondrial inner membrane. PMID:32275929 provides experimental evidence for this localization. Reason: This annotation is well-supported. PMID:32275929 uses BioID and complexome profiling to characterize TMEM70 as an inner mitochondrial membrane protein that interacts with complex I and V. UniProt confirms inner membrane localization with multi-pass topology. Supporting Evidence: PMID:32275929 We here delineate the function of the inner mitochondrial membrane protein TMEM70 |
| GO:0030674 protein-macromolecule adaptor activity | IDA PMID:32275929 TMEM70 functions in the assembly of complexes I and V. | ACCEPT | Summary: This annotation captures the scaffold/adaptor function of TMEM70 in ATP synthase assembly. TMEM70 acts as a scaffold that facilitates membrane insertion and oligomerization of subunit c into the c8-ring. Reason: TMEM70 functions as a scaffold protein that promotes the assembly of the c8-ring by facilitating interaction between subunit c molecules and their membrane insertion. This adaptor activity is its core molecular function. UniProt describes TMEM70 as a "Scaffold protein that participates in the c-ring assembly of mitochondrial ATP synthase". Supporting Evidence: PMID:32275929 This indicates that TMEM70 has a role in the stability of membrane-bound subassemblies or in the membrane recruitment of subunits into the forming complex. |
| GO:0033615 mitochondrial proton-transporting ATP synthase complex assembly | IDA PMID:32275929 TMEM70 functions in the assembly of complexes I and V. | ACCEPT | Summary: This IDA annotation from PMID:32275929 correctly captures the core biological process function of TMEM70 in ATP synthase assembly. This is the primary function of the protein. Reason: PMID:32275929 demonstrates using BioID and complexome profiling that TMEM70 functions in ATP synthase assembly. Loss of TMEM70 results in accumulation of an assembly intermediate followed by reduction of the next assembly intermediate, confirming its role in ATP synthase complex assembly. Supporting Evidence: PMID:32275929 TMEM70 interacts with complex I and V and for both complexes the loss of TMEM70 results in the accumulation of an assembly intermediate followed by a reduction of the next assembly intermediate in the pathway. |
| GO:0032981 mitochondrial respiratory chain complex I assembly | IMP PMID:32275929 TMEM70 functions in the assembly of complexes I and V. | KEEP AS NON CORE | Summary: This annotation reflects the secondary role of TMEM70 in Complex I assembly. TMEM70 interacts with the MCIA complex and its loss affects Complex I levels, though this is secondary to its primary role in ATP synthase assembly. Reason: TMEM70's role in Complex I assembly is secondary to its primary function in ATP synthase assembly. PMID:32275929 shows that loss of TMEM70 affects both Complex I and V, though the effect on Complex V is more pronounced. PMID:33753518 demonstrates that TMEM70 interacts with MCIA complex components (ACAD9, ECSIT, NDUFAF1, TMEM126B). This is a valid annotation but represents a secondary/non-core function. Supporting Evidence: PMID:32275929 TMEM70 interacts with complex I and V and for both complexes the loss of TMEM70 results in the accumulation of an assembly intermediate followed by a reduction of the next assembly intermediate in the pathway. |
| GO:0005739 mitochondrion | HTP PMID:34800366 Quantitative high-confidence human mitochondrial proteome an... | ACCEPT | Summary: This HTP annotation from a quantitative mitochondrial proteome study confirms TMEM70 mitochondrial localization. While correct, this is less specific than the inner membrane localization established by other annotations. Reason: PMID:34800366 is a high-confidence mitochondrial proteome study that correctly identifies TMEM70 as a mitochondrial protein. While less specific than GO:0005743 (mitochondrial inner membrane), this annotation is valid and provides additional proteomics evidence for mitochondrial localization. Supporting Evidence: PMID:34800366 Epub 2021 Nov 19. Quantitative high-confidence human mitochondrial proteome and its dynamics in cellular context. |
| GO:0005515 protein binding | IPI PMID:33359711 TMEM70 forms oligomeric scaffolds within mitochondrial crist... | REMOVE | Summary: This annotation reflects TMEM70 interaction with ATP5MC1 (subunit c). While the interaction is functionally important, GO:0005515 protein binding is too vague. More specific terms like GO:0140260 better capture this interaction. Reason: GO:0005515 protein binding is uninformative. The specific interaction between TMEM70 and ATP5MC1 (subunit c) documented in PMID:33359711 is better captured by GO:0140260 (mitochondrial proton-transporting ATP synthase complex binding) which is already annotated. The functional significance is in facilitating c-ring assembly, not generic protein binding. Supporting Evidence: PMID:33359711 TMEM70 forms oligomeric scaffolds within mitochondrial cristae promoting in situ assembly of mammalian ATP synthase proton channel. |
| GO:0030061 mitochondrial crista | IDA PMID:33359711 TMEM70 forms oligomeric scaffolds within mitochondrial crist... | ACCEPT | Summary: This annotation reflects the specific sub-localization of TMEM70 to mitochondrial cristae where ATP synthase assembly occurs. PMID:33359711 used expansion super-resolution microscopy to demonstrate this localization. Reason: PMID:33359711 provides direct experimental evidence using expansion super-resolution microscopy showing TMEM70 specifically localizes to inner cristae membrane, distinct from MICOS component MIC60. This is functionally relevant as ATP synthase is assembled and enriched at cristae edges. Supporting Evidence: PMID:33359711 we demonstrate using expansion super-resolution microscopy the specific localization of TMEM70 at the inner cristae membrane, distinct from the MICOS component MIC60. |
| GO:0033615 mitochondrial proton-transporting ATP synthase complex assembly | IMP PMID:32275929 TMEM70 functions in the assembly of complexes I and V. | ACCEPT | Summary: This IMP annotation from PMID:32275929 is supported by mutant phenotype analysis showing loss of TMEM70 causes accumulation of assembly intermediates. Core function. Reason: PMID:32275929 demonstrates using complexome profiling that loss of TMEM70 results in accumulation of an assembly intermediate followed by reduction of the next intermediate, providing strong IMP evidence for involvement in ATP synthase complex assembly. Supporting Evidence: PMID:32275929 TMEM70 interacts with complex I and V and for both complexes the loss of TMEM70 results in the accumulation of an assembly intermediate followed by a reduction of the next assembly intermediate in the pathway. |
| GO:0033615 mitochondrial proton-transporting ATP synthase complex assembly | IMP PMID:33359711 TMEM70 forms oligomeric scaffolds within mitochondrial crist... | ACCEPT | Summary: This IMP annotation from PMID:33359711 is based on analysis of cells lacking TMEM70, which show defective c-ring assembly. TMEM70 oligomers provide scaffold for c-ring assembly within cristae. Reason: PMID:33359711 demonstrates that TMEM70 forms oligomeric scaffolds that promote c-ring assembly. Cells lacking TMEM70 show a direct correlation between TMEM70 and subunit c levels, and discrete TMEM70-subunit c complexes with increasing subunit c contents can be detected during assembly. Supporting Evidence: PMID:33359711 our results show that TMEM70 oligomers provide a scaffold for c-ring assembly and that mammalian ATP synthase is assembled within inner cristae membranes. |
| GO:0051260 protein homooligomerization | IDA PMID:33359711 TMEM70 forms oligomeric scaffolds within mitochondrial crist... | ACCEPT | Summary: This annotation correctly captures the oligomerization property of TMEM70. TMEM70 forms large oligomeric scaffolds that are essential for its function in c-ring assembly. Reason: PMID:33359711 demonstrates that TMEM70 forms large oligomers detected by immunoprecipitation and 2D BN/SDS-PAGE. PMID:24576557 also showed TMEM70 detected in multiple forms including dimers on BN-PAGE. This oligomerization is functionally relevant for its scaffold role in c-ring assembly. Supporting Evidence: PMID:33359711 Immunoprecipitation, two-dimensional blue-native/SDS-PAGE, and pulse-chase experiments reveal that TMEM70 forms large oligomers that interact with Su.c not yet incorporated into ATP synthase complexes. |
| GO:0140260 mitochondrial proton-transporting ATP synthase complex binding | IDA PMID:32275929 TMEM70 functions in the assembly of complexes I and V. | ACCEPT | Summary: This annotation accurately captures TMEM70's molecular function of binding to ATP synthase components, specifically subunit c (ATP5MC1/ATP5MC3). This is a core molecular function. Reason: PMID:32275929 and PMID:33753518 demonstrate direct interaction between TMEM70 and ATP synthase subunit c. PMID:33359711 shows TMEM70 oligomers interact with subunit c not yet incorporated into ATP synthase. This specific binding activity is more informative than generic protein binding and represents a core molecular function of TMEM70. Supporting Evidence: PMID:32275929 TMEM70 interacts with complex I and V and for both complexes the loss of TMEM70 results in the accumulation of an assembly intermediate followed by a reduction of the next assembly intermediate in the pathway. |
| GO:0005515 protein binding | IPI PMID:31652072 TMEM70 facilitates biogenesis of mammalian ATP synthase by p... | REMOVE | Summary: This annotation reflects TMEM70 interaction with ATP5MC1 (subunit c) documented in PMID:31652072. While the interaction is real and functionally important, GO:0005515 is too vague. Reason: GO:0005515 protein binding is uninformative. PMID:31652072 documents direct interaction between TMEM70 and subunit c, which is better captured by GO:0140260 (mitochondrial proton-transporting ATP synthase complex binding). The UniProt annotation states TMEM70 "Interacts (homooligomer form) with ATP5MC1". Supporting Evidence: PMID:31652072 Oct 25. TMEM70 facilitates biogenesis of mammalian ATP synthase by promoting subunit c incorporation into the rotor structure of the enzyme. |
| GO:0005743 mitochondrial inner membrane | IDA PMID:24576557 Mitochondrial membrane assembly of TMEM70 protein. | ACCEPT | Summary: This IDA annotation from PMID:24576557 provides direct experimental evidence for TMEM70 inner membrane localization using tagged protein constructs and topology mapping. Reason: PMID:24576557 provides strong experimental evidence for inner membrane localization. The study used tagged forms of TMEM70 to demonstrate hairpin topology with N- and C-termini oriented toward the mitochondrial matrix, consistent with a multi-pass inner membrane protein. Supporting Evidence: PMID:24576557 We used tagged forms of TMEM70 and demonstrated that it has a hairpin structure with the N- and C-termini oriented towards the mitochondrial matrix. |
| GO:0033615 mitochondrial proton-transporting ATP synthase complex assembly | ISS GO_REF:0000024 | ACCEPT | Summary: This ISS annotation based on sequence similarity to mouse ortholog is valid and consistent with extensive experimental evidence for human TMEM70 function. Reason: This ISS annotation inferred from mouse TMEM70 (UniProtKB:Q921N7) is supported by extensive direct experimental evidence in human. TMEM70 function in ATP synthase assembly is conserved across mammals and the annotation is redundant with IDA/IMP evidence from multiple publications. |
| GO:0033615 mitochondrial proton-transporting ATP synthase complex assembly | IMP PMID:31652072 TMEM70 facilitates biogenesis of mammalian ATP synthase by p... | ACCEPT | Summary: This IMP annotation from PMID:31652072 is based on TMEM70 conditional knockout mouse studies showing absence of TMEM70 impairs early stage of ATP synthase biogenesis. Reason: PMID:31652072 provides strong IMP evidence from Tmem70 conditional knockout mice. Loss of TMEM70 prevents incorporation of subunit c into the rotor structure, resulting in incomplete enzyme lacking the Fo proton channel. This is core function evidence. Supporting Evidence: PMID:31652072 absence of TMEM70 impairs the early stage of enzyme biogenesis by preventing incorporation of hydrophobic subunit c into rotor structure of the enzyme. |
| GO:0051259 protein complex oligomerization | IDA PMID:24576557 Mitochondrial membrane assembly of TMEM70 protein. | ACCEPT | Summary: This annotation reflects TMEM70 oligomerization documented in PMID:24576557. TMEM70 was detected in multiple forms including dimers on BN-PAGE, demonstrating self-association. Reason: PMID:24576557 demonstrated TMEM70 detected in multiple forms including dimers on BN-PAGE and confirmed mutual interactions between TMEM70 molecules by immunoprecipitation. This oligomerization is relevant to its scaffold function. Note GO:0051260 protein homooligomerization is also annotated which is more specific. Supporting Evidence: PMID:24576557 On BN-PAGE TMEM70 was detected in multiple forms including dimers and displayed partial overlap with assembled ATP synthase. |
| GO:0005515 protein binding | IPI PMID:33753518 TMEM70 and TMEM242 help to assemble the rotor ring of human ... | REMOVE | Summary: This annotation reflects TMEM70 interactions with subunit c, TMEM242, and MCIA complex components documented in PMID:33753518. While interactions are real, GO:0005515 is uninformative. Reason: GO:0005515 protein binding is too vague. PMID:33753518 identifies specific functionally relevant interactions with ATP5MC3 (subunit c), TMEM242, and MCIA complex components (ACAD9, ECSIT, NDUFAF1, TMEM126B, TIMMDC1). The ATP synthase binding is better captured by GO:0140260. Consider adding specific annotations for MCIA complex interaction if a suitable term exists. Supporting Evidence: PMID:33753518 TMEM70 and TMEM242 help to assemble the rotor ring of human ATP synthase and interact with assembly factors for complex I. |
| GO:0033615 mitochondrial proton-transporting ATP synthase complex assembly | IMP PMID:33753518 TMEM70 and TMEM242 help to assemble the rotor ring of human ... | ACCEPT | Summary: This IMP annotation from PMID:33753518 is based on deletion studies showing TMEM70 and TMEM242 are required for c8-ring assembly and proper ATP synthase levels. Reason: PMID:33753518 provides strong IMP evidence from HAP1 cell knockout studies. Deletion of TMEM70 diminishes ATP synthase content with similar effect on all subunits. Deletion of both TMEM70 and TMEM242 together prevents ATP synthase assembly. This is core function. Supporting Evidence: PMID:33753518 Deletion of TMEM242, similar to deletion of TMEM70, affects but does not completely eliminate the assembly of ATP synthase |
| GO:0031966 mitochondrial membrane | IDA PMID:18953340 TMEM70 mutations cause isolated ATP synthase deficiency and ... | ACCEPT | Summary: This annotation from the original TMEM70 paper establishing its role in ATP synthase deficiency. While correct, this is less specific than inner membrane localization. Reason: PMID:18953340 is the seminal paper identifying TMEM70 mutations as a cause of ATP synthase deficiency. The localization to mitochondrial membrane was part of the initial characterization. While less specific than GO:0005743, this annotation is valid and historically important. Supporting Evidence: PMID:18953340 TMEM70 mutations cause isolated ATP synthase deficiency and neonatal mitochondrial encephalocardiomyopathy. |
| GO:0033615 mitochondrial proton-transporting ATP synthase complex assembly | IMP PMID:18953340 TMEM70 mutations cause isolated ATP synthase deficiency and ... | ACCEPT | Summary: This is the original IMP annotation from the seminal paper identifying TMEM70 as an ATP synthase assembly factor through patient mutation studies. Reason: PMID:18953340 identified TMEM70 mutations as causing isolated ATP synthase deficiency through whole-genome homozygosity mapping and complementation studies. This paper established TMEM70 involvement in ATP synthase biogenesis in higher eukaryotes. Supporting Evidence: PMID:18953340 Complementation of the cell lines of these individuals with wild-type TMEM70 restored biogenesis and metabolic function of the enzyme complex. |
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Download this section (compressed HTML)What is not known — curated, literature-grounded statements of the open unknowns (the inverse of core functions).
Gap: The structural mechanism by which TMEM70 promotes subunit-c membrane insertion, c-ring nucleation, and handoff to TMEM242 remains unresolved.
NARROWING BIOLOGYCURATION MF_DARK
What is known: The review already accepts TMEM70 as an ATP synthase assembly scaffold and ATP synthase complex-binding factor. The gap is the precise structural and temporal mechanism of the TMEM70 oligomer, its transient subunit-c intermediates, and how TMEM242 acts downstream or in parallel.
Significance: Resolving this gap would clarify whether current adaptor/scaffold annotations are sufficient or whether TMEM70 requires a more specific molecular-function term for ATP synthase c-ring assembly assistance.
What would resolve it: Structural studies of TMEM70 with subunit-c intermediates and TMEM242, together with import and pulse-chase assays for defined mutants, should map the sequence of insertion, oligomerization, and handoff events.
Provenance (the field's own admissions):
Gap: TMEM70's reported contribution to respiratory-chain complex I assembly or stability remains difficult to distinguish from secondary effects of complex V failure and cristae disruption.
OPEN BIOLOGYCURATIONONTOLOGY BP_DARK
What is known: The core curated function is mitochondrial ATP synthase complex assembly. Existing evidence also links TMEM70 to MCIA/complex I intermediates, but it is unresolved whether this represents a direct assembly role, shared membrane-subassembly stabilization, or indirect OXPHOS remodeling after complex V biogenesis fails.
Significance: Resolving this gap would determine whether TMEM70 should be annotated to complex I assembly, retained only as complex V assembly factor, or described through a broader mitochondrial membrane-complex biogenesis process.
What would resolve it: Complex-I assembly assays in separation-of-function TMEM70 and TMEM242 mutants, controlled for cristae morphology and ATP synthase abundance, should test whether complex I effects persist independently of complex V defects.
Provenance (the field's own admissions):
Gap: The basis for tissue-specific severity and variable clinical outcome in TMEM70 deficiency remains incompletely understood.
OPEN BIOLOGYCURATION BP_DARK
What is known: TMEM70 disease association and ATP synthase deficiency are well established. The unresolved issue is how residual TMEM70 activity, tissue energy demand, cristae/nucleoid remodeling, secondary OXPHOS effects, and intervention timing combine to produce distinct cardiac, neurologic, and survival outcomes.
Significance: Resolving this gap would improve variant interpretation and avoid over-specific clinical-process annotations that do not distinguish primary ATP synthase assembly failure from downstream tissue pathology.
What would resolve it: Patient genotype-phenotype cohorts, tissue-specific model systems, and calibrated rescue or metabolic-therapy studies should define the amount and timing of TMEM70 activity needed in high-demand tissues.
Provenance (the field's own admissions):
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