mxcQ encodes the sensor histidine kinase component of the MxcQE two-component regulatory system, which functions as a master regulator positioned at the apex of a complex regulatory cascade controlling methanol dehydrogenase gene expression. The protein contains conserved catalytic domains (HisKA and HATPase) that mediate autophosphorylation on a conserved histidine residue and subsequent phosphotransfer to the MxcE response regulator. MxcQ operates in a hierarchical regulatory architecture where MxcQE controls expression of the second two-component system MxbDM, which in turn directly activates mxa operon transcription. MxcQ may integrate signals about lanthanide availability through proposed interactions with apo-XoxF, thereby playing a central role in the lanthanide switch mechanism that determines whether cells express calcium-dependent (MxaFI) or lanthanide-dependent (XoxF) methanol oxidation systems. The sensor kinase is membrane-localized and likely contains transmembrane helices and an extracytoplasmic sensory domain.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0000155 phosphorelay sensor kinase activity | IEA GO_REF:0000002 | ACCEPT | Summary: Correct - MxcQ is the sensor histidine kinase of the MxcQE two-component system, autophosphorylating on a conserved histidine residue and transferring the phosphate to the MxcE response regulator. Falcon deep research independently confirms this organism-specific role, noting MxcQ is "part of the MxcQE two-component system" and is "annotated as a histidine kinase (EC 2.7.13.3 in UniProt)" [file:METEA/mxcQ/mxcQ-deep-research-falcon.md]. Supporting Evidence: file:METEA/mxcQ/mxcQ-claude-deep-research.md sensor histidine kinase component of the MxcQE two-component regulatory system file:METEA/mxcQ/mxcQ-deep-research-falcon.md encodes the sensor histidine kinase component of the file:METEA/mxcQ/mxcQ-deep-research-falcon.md MxcQ is annotated as a |
| GO:0000160 phosphorelay signal transduction system | IEA GO_REF:0000120 | ACCEPT | Summary: Correct - MxcQ participates in a phosphorelay signal transduction system controlling methanol dehydrogenase gene expression through the MxcQE -> MxbDM cascade [file:METEA/mxcQ/mxcQ-claude-deep-research.md, "hierarchical regulatory architecture"]. Falcon deep research confirms the pathway position, noting MxcQ is "part of the MxcQE two-component system" that "regulates expression of mxbDM", and that "MxbDM directly regulates the mxa cluster" [file:METEA/mxcQ/mxcQ-deep-research-falcon.md]. Supporting Evidence: file:METEA/mxcQ/mxcQ-deep-research-falcon.md MxcQE regulates expression of mxbDM file:METEA/mxcQ/mxcQ-deep-research-falcon.md MxbDM directly regulates the mxa cluster file:METEA/mxcQ/mxcQ-deep-research-falcon.md Places MxcQ upstream in the methanol/lanthanide regulatory hierarchy |
| GO:0004672 protein kinase activity | IEA GO_REF:0000117 | KEEP AS NON CORE | Summary: Correct but overly general - More specific term GO:0004673 (protein histidine kinase activity) better captures MxcQ's function. |
| GO:0004673 protein histidine kinase activity | IEA GO_REF:0000003 | ACCEPT | Summary: Correct - MxcQ is a sensor histidine kinase that autophosphorylates on a conserved histidine residue [file:METEA/mxcQ/mxcQ-claude-deep-research.md, "autophosphorylation on this conserved histidine residue"]. Falcon deep research notes MxcQ "is annotated as a histidine kinase (EC 2.7.13.3 in UniProt)" and is the histidine-kinase partner of the MxcQE two-component system [file:METEA/mxcQ/mxcQ-deep-research-falcon.md]. EC 2.7.13.3 (protein-histidine kinase) corresponds to GO:0004673. Supporting Evidence: file:METEA/mxcQ/mxcQ-deep-research-falcon.md histidine kinase** (EC 2.7.13.3 in UniProt) file:METEA/mxcQ/mxcQ-deep-research-falcon.md that autophosphorylates on a conserved histidine and (ii) a |
| GO:0005737 cytoplasm | IEA GO_REF:0000044 | REMOVE | Summary: Incorrect - MxcQ is a membrane-bound sensor kinase, not a cytoplasmic protein. It contains transmembrane helices anchoring it in the cytoplasmic membrane (UniProt C5ASP2 has two predicted TRANSMEM helices at residues 34-55 and 176-199 plus a HAMP domain) [file:METEA/mxcQ/mxcQ-claude-deep-research.md, "membrane-bound histidine kinase"]. Falcon deep research likewise describes MxcQ as a "membrane-associated HK with a periplasmic sensory region and a cytosolic transmitter/kinase region". The Cytoplasm IEA annotation derives from the ARBA NreB-by-homology mapping, which falcon shows does not reflect AM1 biology; membrane (GO:0016020) is the appropriate cellular component. NOTE - this IEA is not negated/NOT in GOA; the cytosolic kinase/transmitter region is intracellular, so the parent "membrane" term plus a more specific "plasma membrane / integral component of membrane" location would be preferable, but a bare GO:0005737 cytoplasm assignment is misleading here. [file:METEA/mxcQ/mxcQ-deep-research-falcon.md]. Supporting Evidence: file:METEA/mxcQ/mxcQ-deep-research-falcon.md membrane-associated HK with a periplasmic sensory region |
| GO:0007165 signal transduction | IEA GO_REF:0000002 | KEEP AS NON CORE | Summary: Correct but very general parent term - More specific phosphorelay signal transduction term better describes MxcQ's function. |
| GO:0016020 membrane | IEA GO_REF:0000120 | ACCEPT | Summary: Correct - MxcQ is a membrane-bound sensor kinase with transmembrane helices [file:METEA/mxcQ/mxcQ-claude-deep-research.md, "membrane-bound histidine kinase" and "transmembrane helices"]. UniProt C5ASP2 has two Phobius-predicted TRANSMEM helices (34-55, 176-199) and an InterPro HAMP domain, and falcon deep research describes MxcQ as a "membrane-associated HK with a periplasmic sensory region", consistent with a membrane location [file:METEA/mxcQ/mxcQ-deep-research-falcon.md]. Supporting Evidence: file:METEA/mxcQ/mxcQ-deep-research-falcon.md membrane-associated HK with a periplasmic sensory region |
| GO:0016301 kinase activity | IEA GO_REF:0000043 | KEEP AS NON CORE | Summary: Correct but general - More specific terms (phosphorelay sensor kinase activity, protein histidine kinase activity) better capture MxcQ's function. |
| GO:0016740 transferase activity | IEA GO_REF:0000043 | KEEP AS NON CORE | Summary: Correct but very general parent term - Kinase activity and phosphorelay sensor kinase activity are more specific. |
| GO:0016772 transferase activity, transferring phosphorus-containing groups | IEA GO_REF:0000002 | KEEP AS NON CORE | Summary: Correct but general - MxcQ transfers phosphate groups from ATP to histidine and then to aspartate on MxcE, but more specific kinase terms better describe this activity. |
| GO:0046983 protein dimerization activity | IEA GO_REF:0000002 | ACCEPT | Summary: Likely correct - Histidine kinases typically function as homodimers with the four-helix bundle domain forming coiled-coil dimers [file:METEA/mxcQ/mxcQ-claude-deep-research.md, "four-helix bundle typically exists as a homodimer"]. |
| GO:0051536 iron-sulfur cluster binding | IEA GO_REF:0000043 | MARK AS OVER ANNOTATED | Summary: Over-annotation from NreB homology - The iron-sulfur cluster annotation traces to UniProt's ARBA mapping of C5ASP2 to the canonical oxygen sensor histidine kinase NreB, which carries an O2-labile [4Fe-4S] cluster. Falcon deep research establishes that the AM1 protein is the MxcQE methanol-oxidation regulator and that "the NreB name [should be treated] as tentative without direct AM1 experimental validation"; critically, the AM1 literature "does not provide AM1-specific biochemical evidence for Fe-S oxygen sensing". No Fe-S binding domain is present in the MxcQ HAMP/HisKA_3/HATPase architecture, so this is a paralog-based over-annotation rather than a demonstrated cofactor [file:METEA/mxcQ/mxcQ-deep-research-falcon.md]. Supporting Evidence: file:METEA/mxcQ/mxcQ-deep-research-falcon.md the NreB name as tentative without direct AM1 experimental validation file:METEA/mxcQ/mxcQ-deep-research-falcon.md does not provide AM1-specific biochemical evidence for Fe–S oxygen sensing |
| GO:0051539 4 iron, 4 sulfur cluster binding | IEA GO_REF:0000043 | MARK AS OVER ANNOTATED | Summary: Over-annotation from NreB homology - Same basis as the parent iron-sulfur cluster binding term. The specific [4Fe-4S] cluster is a hallmark of canonical staphylococcal NreB oxygen sensing (autophosphorylation at H159, transfer to NreC D53, O2-labile cluster), as falcon summarizes for comparison. Falcon concludes the AM1 literature supports MxcQ as a methanol/lanthanide regulatory sensor kinase "without direct evidence of Fe-S cluster-based oxygen sensing by MxcQ", so the inherited 4Fe-4S binding annotation is a paralog-driven over-annotation [file:METEA/mxcQ/mxcQ-deep-research-falcon.md]. Supporting Evidence: file:METEA/mxcQ/mxcQ-deep-research-falcon.md without direct evidence of Fe–S cluster-based oxygen sensing by MxcQ |
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