QmoC (DVU_0850) is the membrane-integral subunit C of the quinone-interacting membrane-bound oxidoreductase (QmoABC) complex in Desulfovibrio vulgaris Hildenborough. The Qmo complex functions as an electron transfer hub in dissimilatory sulfate reduction, transferring electrons from the menaquinone pool to adenylylsulfate (APS) reductase (AprAB). QmoC contains six transmembrane helices and a 4Fe-4S ferredoxin-type domain, serving as the membrane anchor that interfaces with the quinone pool. The protein is essential for the anaerobic electron transport chain during sulfate respiration, connecting cytoplasmic electron donors to the terminal reduction of sulfate. Proteomic and interactome studies in D. vulgaris have validated the physical interaction between the Qmo complex and APS reductase.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0005886 plasma membrane | IEA GO_REF:0000118 | ACCEPT | Summary: QmoC is the membrane-integral subunit of the QmoABC complex. UniProt Phobius predictions identify six transmembrane helices (aa 121-145, 165-186, 238-259, 279-297, 309-329, 341-362). Literature explicitly describes DVU0849-DVU0850 as encoding the quinone-interacting membrane-bound oxidoreductase complex. The deep research file confirms that the Qmo complex is membrane-associated and DVU_0850 is a membrane protein that interfaces with the quinone pool at the cytoplasmic membrane. Reason: Multiple lines of evidence support plasma membrane localization. Phobius prediction of 6 TM helices, InterPro domains including transmembrane di-heme cytochromes (Gene3D 1.20.950.20), and literature explicitly describing Qmo as membrane-bound. This is a core localization for QmoC function. Supporting Evidence: DOI:10.1128/aem.01655-16 DVU0850 Heterodisulfide Reductase, Transmembrane Subunit (Qmo) DOI:10.1128/aem.02469-07 heterodisulfide reductase complex (DVU0848 to DVU0850) file:DESVH/Q72DS9/Q72DS9-deep-research-falcon.md The Qmo complex is membrane-associated; by inference and by the explicit characterization of DVU0849-DVU0850 as coding for the quinone-interacting membrane-bound oxidoreductase complex, DVU_0850 is a membrane protein. |
| GO:0016491 oxidoreductase activity | IEA GO_REF:0000043 | ACCEPT | Summary: QmoC is a subunit of the quinone-interacting membrane-bound oxidoreductase (Qmo) complex. The complex transfers electrons between the quinone pool and APS reductase during dissimilatory sulfate reduction. While this annotation is correct, it is quite broad for a protein with a specific role in electron transfer to APS reductase. Reason: The annotation is accurate as QmoC is part of an oxidoreductase complex. UniProt keywords include "Oxidoreductase" and the protein belongs to the NarG-like superfamily (respiratory nitrate reductase-related). The term captures the general enzymatic category, though more specific terms for electron transfer activity could supplement this. Supporting Evidence: DOI:10.1128/aem.01655-16 DVU0850 Heterodisulfide Reductase, Transmembrane Subunit (Qmo) DOI:10.1002/pmic.200500930 DVU0848-DVU0850 with membrane electron-transfer roles consistent with energy metabolism in DvH |
| GO:0046872 metal ion binding | IEA GO_REF:0000043 | ACCEPT | Summary: QmoC contains a 4Fe-4S ferredoxin-type domain (aa 61-86) and is predicted to bind iron. The protein has UniProt keywords for Iron, Iron-sulfur, and Metal-binding. This is a general parent term that is accurately applied. Reason: The protein clearly binds metal ions through its iron-sulfur cluster. PROSITE patterns PS00198 and PS51379 identify 4Fe-4S binding sites. While more specific child terms (iron ion binding, 4Fe-4S cluster binding) are also annotated, retaining this parent term is appropriate for completeness. Supporting Evidence: UniProt:Q72DS9 DOMAIN 61..86 /note="4Fe-4S ferredoxin-type" /evidence="ECO:0000259|PROSITE:PS51379" |
| GO:0051536 iron-sulfur cluster binding | IEA GO_REF:0000120 | ACCEPT | Summary: QmoC contains an experimentally predicted 4Fe-4S ferredoxin-type domain. InterPro domains include 4Fe4S_Fe-S-bd (IPR017896), 4Fe4S_Fe_S_CS (IPR017900), and HdrC_iron-sulfur_subunit (IPR051460). The Pfam domain Fer4_8 (PF13183) is also present. Reason: Iron-sulfur cluster binding is a core functional property of QmoC. Multiple computational methods predict this binding capacity, which is essential for electron transfer function. This is supported by the more specific 4Fe-4S cluster binding annotation. Supporting Evidence: InterPro:IPR017896 4Fe4S_Fe-S-bd domain InterPro:IPR051460 HdrC_iron-sulfur_subunit domain |
| GO:0051539 4 iron, 4 sulfur cluster binding | IEA GO_REF:0000043 | ACCEPT | Summary: QmoC contains a defined 4Fe-4S ferredoxin-type domain at positions 61-86. This is supported by PROSITE pattern PS00198 (4FE4S_FER_1) and profile PS51379 (4FE4S_FER_2). The protein is also annotated with the helical ferredoxin InterPro domain (IPR009051). Reason: This is a specific and accurate annotation. The 4Fe-4S cluster is essential for the electron transfer function of QmoC within the Qmo complex. Domain predictions from multiple sources (PROSITE, Pfam, InterPro) consistently identify this binding capacity. Supporting Evidence: PROSITE:PS00198 4FE4S_FER_1 pattern match PROSITE:PS51379 4Fe-4S ferredoxin-type domain at positions 61-86 |
| GO:0019645 anaerobic electron transport chain | ISS DOI:10.1128/aem.01655-16 | NEW | Summary: The Qmo complex is part of the anaerobic electron transport chain in sulfate-reducing bacteria. It transfers electrons from the quinone pool to APS reductase during dissimilatory sulfate reduction. Reason: This annotation captures the core biological process in which QmoC participates. The Qmo complex is explicitly part of the respiratory electron transport machinery during anaerobic sulfate respiration. Evidence from the deep research file and publications supports this role. Supporting Evidence: DOI:10.1128/aem.01655-16 Genes coding for electron transfer proteins for sulfate reduction, the Qmo and Dsr AB 428 membrane complexes, were significantly down regulated (Table 3). file:DESVH/Q72DS9/Q72DS9-deep-research-falcon.md DVU_0850 contributes at the membrane quinone interface (Qmo) |
| GO:0019420 dissimilatory sulfate reduction | ISS DOI:10.1128/aem.02469-07 | NEW | Summary: QmoC is essential for dissimilatory sulfate reduction by providing electrons to APS reductase, which catalyzes the first reductive step in the pathway (APS to sulfite). Reason: This is the defining biological process for sulfate-reducing bacteria like D. vulgaris. The Qmo complex is positioned at a critical junction transferring electrons from the quinone pool to APS reductase. Proteomic evidence from PMID:27099342 confirms Qmo-AprA interaction. Supporting Evidence: DOI:10.1128/aem.02469-07 heterodisulfide reductase complex (DVU0848 to DVU0850) under cathodic growth, directly tying the DVU numbering to this organism PMID:27099342 Qmo oxidoreductase and adenyl sulfate reductase alpha subunit |
| GO:0048038 quinone binding | ISS DOI:10.1128/aem.01655-16 | NEW | Summary: As the membrane subunit of the quinone-interacting membrane-bound oxidoreductase complex, QmoC is expected to interact with the quinone pool (menaquinone in D. vulgaris). Reason: The name "quinone-interacting membrane-bound oxidoreductase" explicitly indicates quinone interaction. QmoC is the membrane anchor subunit and thus the primary interface with the membrane-embedded quinone pool. Supporting Evidence: DOI:10.1128/aem.01655-16 the quinone-346 interacting membrane-bound oxidoreductase complex (Qmo) file:DESVH/Q72DS9/Q72DS9-deep-research-falcon.md As a Qmo membrane component, DVU_0850 interfaces with the membrane quinone pool |
| GO:0009055 electron transfer activity | ISS DOI:10.1002/pmic.200500930 | NEW | Summary: QmoC participates in electron transfer from the quinone pool to APS reductase via its iron-sulfur clusters. This electron transfer activity is the primary molecular function of the Qmo complex. Reason: The Qmo complex functions as an electron transfer module. QmoC with its 4Fe-4S cluster and membrane localization facilitates electron flow between the quinone pool and the soluble APS reductase complex. This is a more specific functional annotation than generic oxidoreductase. Supporting Evidence: DOI:10.1002/pmic.200500930 DVU0848-DVU0850 with membrane electron-transfer roles consistent with energy metabolism in DvH |
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