Neurospora crassa CIA30 (Complex I intermediate-associated protein 30, also known as cia35) is a mitochondrial chaperone specifically involved in the assembly of NADH:ubiquinone oxidoreductase (complex I). CIA30 is the founding member of the CIA30/NDUFAF1 family and was identified as one of two novel extra proteins (30 kDa and 84 kDa) that associate with the large membrane arm assembly intermediate of complex I but are not constituent parts of the mature complex (PMID:9769214). Disruption mutants accumulate the matrix arm and the small membrane arm assembly intermediate but cannot form the large membrane arm intermediate. Pulse-chase experiments showed that CIA30 is repeatedly involved in many assembly cycles, consistent with an assembly chaperone role (PMID:9769214). Although called a "chaperone" in the original paper, CIA30 acts specifically as a non-catalytic complex I assembly factor that binds membrane-arm assembly intermediates, not as a general protein-folding chaperone.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0005739 mitochondrion | IBA GO_REF:0000033 | ACCEPT | Summary: IBA annotation for mitochondrion localization. CIA30 is a mitochondrial protein, confirmed by direct experimental evidence (PMID:9769214). UniProt lists mitochondrion as the subcellular location and the protein has a mitochondrial transit peptide (residues 1-8). The IBA annotation is consistent with the IEA annotation from UniProt and the experimental evidence. Reason: Mitochondrial localization is the primary and only documented location of CIA30, directly demonstrated in PMID:9769214. The protein has a mitochondrial transit peptide. Core localization annotation. Supporting Evidence: file:NEUCR/cia30/cia30-deep-research-falcon.md In N. crassa, the cloned CIA30 protein is reported as a globular protein preceded by a typical mitochondrial import sequence of 12 amino acids, supporting mitochondrial targeting and import. |
| GO:0006120 mitochondrial electron transport, NADH to ubiquinone | IBA GO_REF:0000033 | MARK AS OVER ANNOTATED | Summary: IBA annotation for mitochondrial electron transport, NADH to ubiquinone. CIA30 is required for assembly of complex I, which performs NADH:ubiquinone oxidoreduction. Without CIA30, the large membrane arm intermediate cannot be formed, and the mature complex I is not assembled (PMID:9769214). CIA30 is not a subunit of the mature complex but is essential for its assembly. The IBA annotation captures only an indirect (necessity) relationship; CIA30 builds the enzyme but does not itself carry electrons. This row has since disappeared from GOA. Reason: CIA30 is essential for complex I assembly (PMID:9769214), but it is an assembly factor that is absent from the mature complex, so it performs none of the NADH-to-ubiquinone electron transfer steps. Requirement for building the enzyme is captured by GO:0032981; annotating the electron-transport process conflates assembly with participation. Propagation Review Root cause: SOURCE STALE OR MISSING Failure modes: ROLE CONFLATION Sources checked: PANTHER:PTN000324265 · PANTHER:PTN000324265 SOURCE STALE OR MISSING GO:0006120 is no longer propagated to cia30 from this node in the current GOA snapshot; the assembly-process IBD (GO:0032981 lineage) is the appropriate family-level statement for a non-subunit assembly factor. Supporting Evidence: PMID:9769214 Mutants generated by disrupting the genes of either of the two proteins accumulate the matrix arm of complex I and the small membrane arm assembly intermediate, but are incapable of forming the large intermediate |
| GO:0010257 NADH dehydrogenase complex assembly | IBA GO_REF:0000033 | ACCEPT | Summary: IBA annotation for NADH dehydrogenase complex assembly. This is the core biological process function of CIA30. PMID:9769214 directly demonstrated that CIA30 is required for assembly of the large membrane arm intermediate of complex I, and pulse-chase experiments showed it participates in repeated assembly cycles. The IBA annotation is consistent with the NAS annotation for the more specific GO:0032981 term. Reason: NADH dehydrogenase complex assembly is the core function of CIA30. Directly demonstrated by disruption mutants that fail to form the large membrane arm intermediate (PMID:9769214). The IBA is well supported and phylogenetically appropriate for the CIA30/NDUFAF1 family. Current PAINT places an IRD (NOT) for this term at PTN000995776 (2026-02-10), a fungal CIA30/NDUFAF1 clade that includes N. crassa cia30, so this IBA is no longer propagated by PAINT and remains only in the cached GOA file. The IRD is contradicted for this protein: cia30 disruption blocks assembly of the complex I membrane arm (PMID:9769214), so the ACCEPT stands and the IRD is listed in projects/IRD_EVIDENCE/PAINT_REPORT.md. Propagation Review Root cause: NO FAILURE CORE Supporting Evidence: PMID:9769214 Mutants generated by disrupting the genes of either of the two proteins accumulate the matrix arm of complex I and the small membrane arm assembly intermediate, but are incapable of forming the large intermediate PMID:9769214 Pulse-chase labelling experiments showed that the two proteins are repeatedly involved in many assembly cycles of the intermediate file:NEUCR/cia30/cia30-deep-research-falcon.md Neurospora complex I assembly was established to occur stepwise from intermediates. CIA30 (together with CIA84) is associated with the large membrane-arm assembly intermediate and is not found in the mature complex I holoenzyme. |
| GO:0051082 unfolded protein binding | IBA GO_REF:0000033 | MARK AS OVER ANNOTATED | Summary: IBA annotation for unfolded protein binding. GO:0051082 is now formally obsolete (go-ontology#30962). CIA30 was described as a "novel chaperone" in the original publication (PMID:9769214), but its function is specifically as a complex I assembly factor, not as a general unfolded protein binding protein. CIA30 associates exclusively with the large membrane arm assembly intermediate of complex I and participates in repeated assembly cycles (PMID:9769214). This is a specific assembly chaperone function rather than general unfolded protein binding. The term "chaperone" as used in the original paper refers to the specific assembly assistance role, not to broad unfolded protein recognition. Per UPB project rules, specific assembly chaperones that are not general unfolded protein binding proteins should be marked as over-annotated or modified. Reason: CIA30 is a specific complex I assembly factor, not a general unfolded protein binding protein. While described as a "chaperone" in PMID:9769214, this refers to its specific role in complex I membrane arm assembly -- it associates exclusively with the large membrane arm assembly intermediate and does not bind unfolded proteins generally. The GO:0051082 annotation overstates the generality of CIA30's binding specificity. The complex I assembly function is already captured by GO:0010257 and GO:0032981. Propagation Review Root cause: SOURCE STALE OR MISSING Failure modes: SOURCE EVIDENCE WEAK Sources checked: PANTHER:PTN000324265 · PANTHER:PTN000324265 SOURCE STALE OR MISSING GO:0051082 is obsolete and this propagation is absent from the current GOA snapshot; the family-level claim of unfolded-client binding was never supported by assays of client conformational state. Supporting Evidence: PMID:9769214 In the wild-type, the extra proteins exclusively associate with the large membrane arm assembly intermediate PMID:9769214 These results indicate that the two proteins are novel chaperones specific for complex I membrane arm assembly file:NEUCR/cia30/cia30-deep-research-falcon.md The strongest organism-specific evidence indicates CIA30 is imported into mitochondria, exists in free and assembly-bound pools, and binds transiently to a large membrane-arm assembly intermediate (not the mature holoenzyme). |
| GO:0005739 mitochondrion | IEA GO_REF:0000044 | ACCEPT | Summary: IEA annotation for mitochondrion from UniProt subcellular location mapping. Consistent with the IBA annotation for the same term and the direct experimental evidence from PMID:9769214. UniProt lists mitochondrion as the subcellular location. Reason: Consistent with IBA annotation and direct experimental evidence. Mitochondrion is the primary and only documented location of CIA30. |
| GO:0032981 mitochondrial respiratory chain complex I assembly | NAS PMID:9769214 Involvement of two novel chaperones in the assembly of mitoc... | ACCEPT | Summary: NAS annotation for mitochondrial respiratory chain complex I assembly from PMID:9769214. This is the core biological process function of CIA30. The original paper titled "Involvement of two novel chaperones in the assembly of mitochondrial NADH:Ubiquinone oxidoreductase (complex I)" directly describes the role of CIA30 in complex I assembly. The NAS evidence code is appropriate as the paper provides direct experimental evidence for complex I assembly involvement. This is a more specific child of GO:0010257. Reason: Complex I assembly is the core function of CIA30. PMID:9769214 directly demonstrated this through disruption mutants, pulse-chase experiments, and co-purification with assembly intermediates. This more specific term (child of GO:0010257) appropriately captures the respiratory chain complex I assembly function. Supporting Evidence: PMID:9769214 These results indicate that the two proteins are novel chaperones specific for complex I membrane arm assembly |
| GO:0051082 unfolded protein binding | IDA PMID:9769214 Involvement of two novel chaperones in the assembly of mitoc... | MARK AS OVER ANNOTATED | Summary: IDA annotation for unfolded protein binding from PMID:9769214. GO:0051082 is now formally obsolete (go-ontology#30962). The original paper demonstrated that CIA30 associates with the large membrane arm assembly intermediate of complex I and is involved in repeated assembly cycles (PMID:9769214: "the extra proteins exclusively associate with the large membrane arm assembly intermediate" and "Pulse-chase labelling experiments showed that the two proteins are repeatedly involved in many assembly cycles"). The authors called CIA30 a "chaperone" but specified it was "specific for complex I membrane arm assembly." This is a specific assembly factor function, not general unfolded protein binding. The protein does not bind unfolded proteins broadly -- it binds specifically to complex I assembly intermediates. The IDA evidence demonstrates complex I assembly intermediate binding, not general unfolded protein binding. Reason: The IDA evidence from PMID:9769214 demonstrates that CIA30 binds specifically to complex I assembly intermediates, not to unfolded proteins generally. The original paper explicitly states the proteins are "chaperones specific for complex I membrane arm assembly." GO:0051082 overstates the generality of the binding. The complex I assembly function is better captured by GO:0032981 and GO:0010257. While CIA30 may indeed interact with unfolded or partially assembled complex I subunits, calling this "unfolded protein binding" conflates a specific assembly factor role with general chaperone function. Supporting Evidence: PMID:9769214 In the wild-type, the extra proteins exclusively associate with the large membrane arm assembly intermediate PMID:9769214 Pulse-chase labelling experiments showed that the two proteins are repeatedly involved in many assembly cycles of the intermediate PMID:9769214 These results indicate that the two proteins are novel chaperones specific for complex I membrane arm assembly |
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