ATP6V0E1 encodes V-type proton ATPase subunit e 1 (81 amino acids, 9.2 kDa), a small dual-transmembrane protein that is a structural component of the V0 membrane-embedded domain of the vacuolar-type H+-ATPase (V-ATPase). The V0 complex contains the proton transport subunit a, a proteolipid c-ring, rotary subunit d, subunits e and f, and accessory subunits ATP6AP1 and ATP6AP2. Subunit e 1 has an N-terminal lumenal segment, two transmembrane helices, a short cytoplasmic loop, and a C-terminal lumenal tail bearing an N-linked glycan at Asn70 that contributes to V-ATPase assembly and stability. Humans have two paralogous e subunits: ATP6V0E1 (e1, ubiquitous) and ATP6V0E2 (e2, restricted to kidney and brain). Both isoforms can complement a yeast e subunit deletion, confirming that the e subunit is essential for proton pump function. ATP6V0E1 localizes to lysosomal and endosomal membranes as part of the assembled V-ATPase holoenzyme. As a V0 structural subunit, it contributes to the proton translocation function of the V-ATPase complex that acidifies lysosomes, endosomes, and other intracellular compartments.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:1902600 proton transmembrane transport | IBA GO_REF:0000033 | ACCEPT | Summary: IBA phylogenetic transfer; proton transmembrane transport is the core function of the V-ATPase, and subunit e1 is required for this activity. Reason: Proton transmembrane transport is the fundamental process of the V-ATPase. Both e1 and e2 are essential for proton pump function as shown by yeast complementation (PMID:17350184). |
| GO:0000220 vacuolar proton-transporting V-type ATPase, V0 domain | IBA GO_REF:0000033 | ACCEPT | Summary: IBA phylogenetic transfer; V0 domain membership is confirmed by cryo-EM structure (PMID:33065002). Reason: ATP6V0E1 is a confirmed V0 domain component as shown by cryo-EM structures of the complete human V-ATPase (PMID:33065002). Supporting Evidence: file:human/ATP6V0E1/ATP6V0E1-uniprot.txt The proton translocation complex V0 consists of the proton transport subunit a, a ring of proteolipid subunits c9c'', rotary subunit d, subunits e and f, and the accessory subunits ATP6AP1/Ac45 and ATP6AP2/PRR |
| GO:0016020 membrane | IEA GO_REF:0000044 | MODIFY | Summary: IEA from UniProt keyword mapping; generic membrane term consistent with dual-transmembrane topology of e1 subunit. Reason: Generic membrane is less informative than the more specific lysosomal and endosomal membrane annotations already present. The dual-TM topology and V0 domain membership place it specifically at vesicular membranes. Proposed replacements: lysosomal membrane |
| GO:0033179 proton-transporting V-type ATPase, V0 domain | IEA GO_REF:0000002 | ACCEPT | Summary: IEA from InterPro; V0 domain membership is experimentally confirmed. Reason: V0 domain membership is directly confirmed by cryo-EM structures (PMID:33065002). |
| GO:0046961 proton-transporting ATPase activity, rotational mechanism | IEA GO_REF:0000002 | ACCEPT | Summary: IEA from InterPro; rotational mechanism ATPase activity is the complex-level activity to which e1 contributes. Reason: The V-ATPase employs a rotational mechanism. Subunit e1 as a V0 structural component contributes to this activity. The annotation is appropriate with contributes_to semantics implied. |
| GO:1902600 proton transmembrane transport | IEA GO_REF:0000002 | ACCEPT | Summary: IEA from InterPro; consistent with IBA and IGI evidence for proton transport role. Reason: Proton transmembrane transport is the core function. Multiple lines of evidence support this annotation. |
| GO:0005515 protein binding | IPI PMID:32296183 A reference map of the human binary protein interactome. | MARK AS OVER ANNOTATED | Summary: Generic protein binding from high-throughput binary interactome; uninformative. Reason: High-throughput interactome data; protein binding does not capture the specific V0 structural role of e1. |
| GO:0005765 lysosomal membrane | TAS Reactome:R-HSA-9639286 | ACCEPT | Summary: Reactome TAS for lysosomal membrane localization; consistent with V0 component localization. Reason: Lysosomal membrane is the primary functional localization of the assembled V-ATPase V0 domain. |
| GO:0005765 lysosomal membrane | TAS Reactome:R-HSA-9640167 | ACCEPT | Summary: Reactome TAS for lysosomal membrane; consistent. Reason: Lysosomal membrane localization; consistent. |
| GO:0005765 lysosomal membrane | TAS Reactome:R-HSA-9640168 | ACCEPT | Summary: Reactome TAS for lysosomal membrane; consistent. Reason: Lysosomal membrane localization; consistent. |
| GO:0005765 lysosomal membrane | TAS Reactome:R-HSA-9640175 | ACCEPT | Summary: Reactome TAS for lysosomal membrane; consistent. Reason: Lysosomal membrane localization; consistent. |
| GO:0005765 lysosomal membrane | TAS Reactome:R-HSA-9640195 | ACCEPT | Summary: Reactome TAS for lysosomal membrane; consistent. Reason: Lysosomal membrane localization; consistent. |
| GO:0005765 lysosomal membrane | TAS Reactome:R-HSA-9645598 | ACCEPT | Summary: Reactome TAS for lysosomal membrane; consistent. Reason: Lysosomal membrane localization; consistent. |
| GO:0005765 lysosomal membrane | TAS Reactome:R-HSA-9645608 | ACCEPT | Summary: Reactome TAS for lysosomal membrane; consistent. Reason: Lysosomal membrane localization; consistent. |
| GO:0005765 lysosomal membrane | TAS Reactome:R-HSA-9646468 | ACCEPT | Summary: Reactome TAS for lysosomal membrane; consistent. Reason: Lysosomal membrane localization; consistent. |
| GO:0005765 lysosomal membrane | TAS Reactome:R-HSA-9858941 | ACCEPT | Summary: Reactome TAS for lysosomal membrane in MITF-dependent lysosome biogenesis context; consistent. Reason: Lysosomal membrane localization consistent with V0 domain subunit function. |
| GO:0046961 proton-transporting ATPase activity, rotational mechanism | IGI PMID:17350184 Molecular cloning and characterization of a novel form of th... | ACCEPT | Summary: IGI evidence from yeast complementation showing both e1 and e2 are essential for proton pump function; supports ATPase rotational mechanism activity. Reason: Blake-Palmer et al. 2007 showed that either e1 or e2 can complement yeast lacking the e subunit ortholog, directly demonstrating the essential role of the e subunit in proton pump function. This is valid IGI evidence. Supporting Evidence: PMID:17350184 complementation studies in a yeast strain deficient for the ortholog of this subunit, that either form of the e-subunit is essential for proper proton pump function |
| GO:1902600 proton transmembrane transport | IGI PMID:17350184 Molecular cloning and characterization of a novel form of th... | ACCEPT | Summary: IGI evidence from yeast complementation; same rationale as GO:0046961 IGI above. Reason: Yeast complementation study directly demonstrates the e subunit is essential for proton pump function (PMID:17350184). IGI annotation is well supported. Supporting Evidence: PMID:17350184 complementation studies in a yeast strain deficient for the ortholog of this subunit, that either form of the e-subunit is essential for proper proton pump function |
| GO:0016241 regulation of macroautophagy | NAS PMID:22982048 Lipofuscin is formed independently of macroautophagy and lys... | MARK AS OVER ANNOTATED | Summary: NAS annotation; cited paper uses V-ATPase disruption as a tool to impair lysosomal function. Does not specifically implicate e1 subunit in macroautophagy regulation. Reason: The cited paper does not demonstrate that ATP6V0E1 specifically regulates macroautophagy; it uses generic V-ATPase disruption to block lysosomal activity. This is an over-annotation of a generic downstream consequence of V-ATPase disruption. |
| GO:0030670 phagocytic vesicle membrane | TAS Reactome:R-HSA-1222516 | KEEP AS NON CORE | Summary: Reactome TAS for phagocytic vesicle membrane (intraphagosomal pH lowering context); consistent with V0 domain at phagocytic vesicles in immune cells. Reason: Phagocytic vesicle membrane localization is a non-core context for this ubiquitous V0 subunit. The primary core localizations are lysosomal and endosomal membranes. |
| GO:0010008 endosome membrane | TAS Reactome:R-HSA-5252133 | ACCEPT | Summary: Reactome TAS for endosome membrane; consistent with V0 component at endosomal membranes where V-ATPase acidifies endosomes. Reason: Endosomal membrane localization is a core location for the V-ATPase V0 domain; required for endosomal acidification and receptor recycling. |
| GO:0010008 endosome membrane | TAS Reactome:R-HSA-74723 | ACCEPT | Summary: Reactome TAS for endosome membrane in endosome acidification context; consistent. Reason: Endosome membrane localization; consistent with V-ATPase function. |
| GO:0010008 endosome membrane | TAS Reactome:R-HSA-917841 | ACCEPT | Summary: Reactome TAS for endosome membrane in transferrin acidification context; consistent. Reason: Endosome membrane localization in transferrin endocytosis context; consistent with V-ATPase function. |
| GO:0007035 vacuolar acidification | ISS GO_REF:0000024 | ACCEPT | Summary: ISS manual ortholog transfer; vacuolar acidification is the core downstream function of V-ATPase activity. Reason: Vacuolar acidification is the primary biological process driven by the V-ATPase. As a required V0 structural subunit, e1 is appropriately annotated to this process. |
| GO:0042625 ATPase-coupled ion transmembrane transporter activity | ISS GO_REF:0000024 | ACCEPT | Summary: ISS manual ortholog transfer; ATPase-coupled ion transmembrane transporter activity is an appropriate broader molecular function term for the V-ATPase proton translocation activity. Reason: ATPase-coupled ion transmembrane transporter activity describes the complex-level molecular function that e1 contributes to as a V0 structural component. Appropriate with contributes_to semantics. |
| GO:0046961 proton-transporting ATPase activity, rotational mechanism | TAS PMID:9556572 Identification and characterization of a novel 9.2-kDa membr... | ACCEPT | Summary: TAS from Ludwig et al. 1998 original characterization of M9.2 (e1) protein in bovine V-ATPase; establishes e1 as a V-ATPase membrane sector component with rotational proton transport activity. Reason: The original characterization paper identified M9.2 (e1) as a V-ATPase membrane sector component, supporting proton-transporting ATPase activity annotation. The e subunit is part of the V0 sector responsible for proton translocation. Supporting Evidence: PMID:9556572 M9.2, a novel extremely hydrophobic 9.2-kDa protein comprising 80 amino acids, was detected in the membrane sector |
| GO:1902600 proton transmembrane transport | TAS PMID:9556572 Identification and characterization of a novel 9.2-kDa membr... | ACCEPT | Summary: TAS from original M9.2 characterization; proton transmembrane transport is the core function. Reason: The original characterization places e1 (M9.2) in the V-ATPase membrane sector responsible for proton transport. Supporting Evidence: PMID:9556572 M9.2, a novel extremely hydrophobic 9.2-kDa protein comprising 80 amino acids, was detected in the membrane sector |
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Download this section (compressed HTML)Q: What is the precise structural function of the e subunit within the V0 complex — does it contribute to c-ring stability, the a subunit interface, or the assembly pathway of V0?
Suggested experts: Wang L, Rubinstein JL
Q: Does the N-linked glycan on Asn70 of e1 have a specific structural role (as part of the luminal glycan coat) in V-ATPase folding or targeting, and does loss of this glycosylation site affect V-ATPase function or localization?
Suggested experts: Wang L, Fu TM
Experiment: Generate ATP6V0E1 Asn70Gln (N70Q) glycosylation-null mutant by CRISPR/HDR and assess V-ATPase holoenzyme assembly, lysosomal membrane targeting, and lysosomal acidification function compared to wild-type cells.
Hypothesis: The N-linked glycan at Asn70 of ATP6V0E1 is required for efficient V-ATPase assembly or lysosomal targeting.
Type: CRISPR knock-in and V-ATPase assembly/acidification assay
Experiment: Using isoform-specific antibodies or endogenous tagging of each paralog in the same cell line, determine whether e1- and e2-containing V-ATPase complexes have distinct subcellular distributions (lysosomal vs endosomal vs plasma membrane) and whether V1/V0 assembly stoichiometry differs between the isoforms.
Hypothesis: ATP6V0E1 (e1) and ATP6V0E2 (e2) confer different targeting or functional properties to V-ATPase complexes in the same cell type.
Type: isoform-specific localization and V-ATPase complex stoichiometry
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