NDUFB11 (also known as ESSS / Complex I-ESSS, and neuronal protein 17.3) is a small, X-linked, nuclear-encoded accessory (supernumerary) subunit of mitochondrial respiratory chain Complex I (NADH:ubiquinone oxidoreductase). It is a genuine, stable structural component of the mature 45-subunit holoenzyme that is not itself involved in catalysis; its role is to help assemble and stabilize the membrane (proximal) arm of the complex. The mature protein is imported via an N-terminal mitochondrial transit peptide and is anchored in the mitochondrial inner membrane by a single transmembrane helix. By supporting a functional Complex I, NDUFB11 contributes to electron transfer from NADH to ubiquinone and thereby to oxidative phosphorylation. Loss-of-function variants cause isolated mitochondrial complex I deficiency and X-linked syndromic disorders including microphthalmia with linear skin defects (MLS-like / LSDMCA3) and histiocytoid cardiomyopathy, reflecting its requirement for a functional respiratory chain.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0045271 respiratory chain complex I | IBA GO_REF:0000033 | ACCEPT | Summary: Phylogenetic (IBA) inference that NDUFB11 is part_of respiratory chain complex I. This is the correct, well-supported cellular-component/complex-membership assignment for this accessory subunit and is independently confirmed experimentally (IDA/IPI below). Core to its function. |
| GO:0005743 mitochondrial inner membrane | IEA GO_REF:0000044 | KEEP AS NON CORE | Summary: Electronic (UniProt SubCell mapping) location in the mitochondrial inner membrane. Consistent with the UniProt-curated location and with the single predicted transmembrane helix; redundant with the EXP/IDA rows but correct. Retained as a supporting location assertion. |
| GO:0005515 protein binding | IPI PMID:25416956 A proteome-scale map of the human interactome network. | MARK AS OVER ANNOTATED | Summary: Bare "protein binding" from a proteome-scale binary interactome map (partner FATE1, UniProtKB:Q969F0). The interaction is real interactome data but "protein binding" is uninformative about NDUFB11's molecular function, and this high-throughput partner has no established Complex-I-related role. Over-annotation. |
| GO:0005515 protein binding | IPI PMID:32296183 A reference map of the human binary protein interactome. | MARK AS OVER ANNOTATED | Summary: Bare "protein binding" from the HuRI reference binary interactome (partners include GPR42, CLDN7, GJB1, HIBADH, EBP, GPR152, FATE1, GPR101, and the Complex I assembly factor TIMMDC1). While TIMMDC1 is a biologically plausible partner, "protein binding" as an enables MF is uninformative for this structural subunit. Over-annotation. |
| GO:0005515 protein binding | IPI PMID:33961781 Dual proteome-scale networks reveal cell-specific remodeling... | MARK AS OVER ANNOTATED | Summary: Bare "protein binding" from a proteome-scale interactome network (partner TIMMDC1, UniProtKB:Q9NPL8, a Complex I assembly factor). Interaction is plausible in an assembly context but "protein binding" does not capture a molecular function. Over-annotation. |
| GO:0005743 mitochondrial inner membrane | IDA PMID:28844695 Architecture of Human Mitochondrial Respiratory Megacomplex ... | ACCEPT | Summary: Direct-assay (ComplexPortal, cryo-EM megacomplex study) location in the mitochondrial inner membrane. NDUFB11 is resolved as a membrane-arm subunit of Complex I in the respiratory megacomplex, consistent with an inner-membrane location. Correct and experimentally grounded. |
| GO:0009060 aerobic respiration | NAS PMID:30030361 Assembly of mammalian oxidative phosphorylation complexes I-... | KEEP AS NON CORE | Summary: Non-traceable author statement (ComplexPortal) associating the Complex I holoenzyme with aerobic respiration. This is a true complex-level process but is broader than NDUFB11's specific structural role; the honest gene-level process terms are Complex I assembly (GO:0032981) and NADH-to-ubiquinone electron transport (GO:0006120). Kept as non-core context. |
| GO:0042776 proton motive force-driven mitochondrial ATP synthesis | NAS PMID:30030361 Assembly of mammalian oxidative phosphorylation complexes I-... | MARK AS OVER ANNOTATED | Summary: Non-traceable author statement (ComplexPortal) linking the OXPHOS system to proton-motive-force-driven ATP synthesis. ATP synthesis is downstream of Complex I and is carried out by Complex V; this is a holoenzyme/pathway-level annotation that over-reaches for an individual Complex I accessory subunit. Marked as over-annotated. |
| GO:0045271 respiratory chain complex I | IPI PMID:28844695 Architecture of Human Mitochondrial Respiratory Megacomplex ... | ACCEPT | Summary: Physical-interaction evidence (ComplexPortal) that NDUFB11 is part_of respiratory chain complex I, from cryo-EM of the human respiratory megacomplex in which the subunit is directly assigned. Core complex-membership annotation. |
| GO:0005739 mitochondrion | IDA GO_REF:0000052 | KEEP AS NON CORE | Summary: Immunofluorescence (HPA) localization to mitochondrion. Correct but less specific than the mitochondrial inner membrane annotations; retained as a coarse-grained location. |
| GO:0005739 mitochondrion | HTP PMID:34800366 Quantitative high-confidence human mitochondrial proteome an... | KEEP AS NON CORE | Summary: High-throughput mitochondrial proteome study localizing NDUFB11 to mitochondrion. Consistent with all other evidence; less specific than the inner-membrane annotations. Kept as non-core. |
| GO:0005743 mitochondrial inner membrane | EXP PMID:31206022 BAP31 regulates mitochondrial function via interaction with ... | ACCEPT | Summary: Experimental subcellular-location evidence (Namba 2019) placing NDUFB11 in the mitochondrial inner membrane; this is one of the UniProt-cited sources for the curated inner-membrane location. Correct and experimentally supported. |
| GO:0045271 respiratory chain complex I | IDA PMID:12611891 The subunit composition of the human NADH dehydrogenase obta... | ACCEPT | Summary: Direct assay: NDUFB11 (as the ESSS/Np17.3 subunit) was identified by mass spectrometry in immunopurified human Complex I, establishing it as an integral subunit of the holoenzyme. This is a foundational, core complex-membership annotation. |
| GO:0045271 respiratory chain complex I | IDA PMID:27626371 Accessory subunits are integral for assembly and function of... | ACCEPT | Summary: Direct assay (Stroud et al. 2016): gene-editing knockout and quantitative proteomics established NDUFB11 as an accessory subunit integral to assembly and function of human Complex I. This is the primary experimental anchor for complex-membership and function; core. |
| GO:0005515 protein binding | IPI PMID:31206022 BAP31 regulates mitochondrial function via interaction with ... | MARK AS OVER ANNOTATED | Summary: Bare "protein binding" (partner BCAP31/BAP31, UniProtKB:P51572), the interaction curated in UniProt (Interacts with BCAP31). Biologically meaningful in the context of ER-mitochondria-mediated Complex I biogenesis, but "protein binding" does not convey a molecular function for NDUFB11. Over-annotation. |
| GO:0005739 mitochondrion | IDA PMID:31206022 BAP31 regulates mitochondrial function via interaction with ... | KEEP AS NON CORE | Summary: Direct-assay mitochondrial localization from the same study (Namba 2019). Correct but less specific than the inner-membrane annotation from the same reference. Kept as non-core. |
| GO:0005743 mitochondrial inner membrane | TAS Reactome:R-HSA-163217 | KEEP AS NON CORE | Summary: Reactome (TAS) inner-membrane location associated with the Complex-I catalytic reaction. Correct location; redundant with the EXP/IDA/IEA rows. Retained as non-core. |
| GO:0005743 mitochondrial inner membrane | TAS Reactome:R-HSA-6799178 | KEEP AS NON CORE | Summary: Reactome (TAS) inner-membrane location from a Complex I biogenesis reaction. Correct but redundant location annotation. Non-core. |
| GO:0005743 mitochondrial inner membrane | TAS Reactome:R-HSA-6799179 | KEEP AS NON CORE | Summary: Reactome (TAS) inner-membrane location from a Complex I biogenesis reaction. Correct but redundant location annotation. Non-core. |
| GO:0005743 mitochondrial inner membrane | TAS Reactome:R-HSA-6799191 | KEEP AS NON CORE | Summary: Reactome (TAS) inner-membrane location from a Complex I biogenesis reaction. Correct but redundant location annotation. Non-core. |
| GO:0005743 mitochondrial inner membrane | TAS Reactome:R-HSA-6799196 | KEEP AS NON CORE | Summary: Reactome (TAS) inner-membrane location from the Complex I biogenesis pathway (final assembly step). Correct but redundant location annotation. Non-core. |
| GO:0005743 mitochondrial inner membrane | TAS Reactome:R-HSA-6799197 | KEEP AS NON CORE | Summary: Reactome (TAS) inner-membrane location from a Complex I biogenesis reaction. Correct but redundant location annotation. Non-core. |
| GO:0005743 mitochondrial inner membrane | TAS Reactome:R-HSA-6799202 | KEEP AS NON CORE | Summary: Reactome (TAS) inner-membrane location from a Complex I biogenesis reaction. Correct but redundant location annotation. Non-core. |
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