CysNC is the GTPase-containing regulatory subunit 1 of the proteobacterial sulfate adenylyltransferase complex. It couples GTP hydrolysis to the CysD reaction that converts sulfate and ATP to APS. The protein also carries a C-terminal APS-kinase-like domain, but the catalytic contribution of that domain to the KT2440 complex remains unresolved.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0000103 sulfate assimilation | IEA GO_REF:0000104 | ACCEPT | Summary: CysNC supplies GTP-coupled sulfate activation. Reason: GTP hydrolysis by the CysN portion couples energy to the CysD sulfate-adenylation step, directly contributing to sulfate assimilation and downstream sulfide synthesis. Primary structural evidence is from P. syringae and applied by conserved subunit architecture. Supporting Evidence: PMID:16387658 coupling the energy of GTP hydrolysis to APS formation. PMID:16387658 the X-ray crystal structure of a complex between Pseudomonas syringae ATPS (CysD) and its associated regulatory G protein (CysN). |
| GO:0003924 GTPase activity | IEA GO_REF:0000120 | ACCEPT | Summary: The CysN domain is a regulatory GTPase. Reason: The G protein hydrolyzes GTP and couples its turnover to CysD catalysis. This is the intrinsic activity of the subunit, not ATP sulfurylase chemistry carried out in isolation. Supporting Evidence: PMID:16387658 coupling the energy of GTP hydrolysis to APS formation. PMID:16387658 the X-ray crystal structure of a complex between Pseudomonas syringae ATPS (CysD) and its associated regulatory G protein (CysN). |
| GO:0004781 sulfate adenylyltransferase (ATP) activity | IEA GO_REF:0000120 | ACCEPT | Summary: CysNC contributes to ATP sulfurylase activity within the complex. Reason: The complex-level activity is biologically correct: CysNC supplies the coupled GTPase function. The review does not alter machine qualifiers; core_functions records the contribution to the complex reaction separately from intrinsic GTPase activity. Supporting Evidence: PMID:16387658 coupling the energy of GTP hydrolysis to APS formation. PMID:16387658 the X-ray crystal structure of a complex between Pseudomonas syringae ATPS (CysD) and its associated regulatory G protein (CysN). |
| GO:0005525 GTP binding | IEA GO_REF:0000120 | ACCEPT | Summary: GTP binding is integral to the regulatory GTPase cycle. Reason: Nucleotide binding supports the core CysN energy-coupling mechanism, rather than a peripheral function. Supporting Evidence: PMID:16387658 coupling the energy of GTP hydrolysis to APS formation. PMID:16387658 the X-ray crystal structure of a complex between Pseudomonas syringae ATPS (CysD) and its associated regulatory G protein (CysN). |
| GO:0006790 sulfur compound metabolic process | IEA GO_REF:0000002 | MODIFY | Summary: Refine sulfur metabolism to sulfate assimilation. Reason: The known contribution is the activation step of sulfate assimilation; the broad parent is true and should be refined rather than rejected. Proposed replacements: sulfate assimilation Supporting Evidence: PMID:16387658 coupling the energy of GTP hydrolysis to APS formation. |
| GO:0070814 hydrogen sulfide biosynthetic process | IEA GO_REF:0000120 | ACCEPT | Summary: CysNC supplies GTP-coupled sulfate activation. Reason: GTP hydrolysis by the CysN portion couples energy to the CysD sulfate-adenylation step, directly contributing to sulfate assimilation and downstream sulfide synthesis. Primary structural evidence is from P. syringae and applied by conserved subunit architecture. Supporting Evidence: PMID:16387658 coupling the energy of GTP hydrolysis to APS formation. PMID:16387658 the X-ray crystal structure of a complex between Pseudomonas syringae ATPS (CysD) and its associated regulatory G protein (CysN). |
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Download this section (compressed HTML)Q: Is the C-terminal APS-kinase-like domain of Q88NA8 catalytically active, or is it a retained but inactive fusion remnant in the direct APS-reduction route?
Experiment: Reconstitute Q88NA8/Q88NA9 and quantify both APS and PAPS formation, then test isolated C-terminal-domain and active-site variants for APS kinase activity.
Type: pathway reconstitution and domain-function assay
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