moaA encodes the canonical radical-SAM GTP 3',8'-cyclase of Pseudomonas putida KT2440. It binds two [4Fe-4S] clusters and converts GTP to the cyclic intermediate that MoaC rearranges to cyclic pyranopterin monophosphate during the first stage of molybdenum-cofactor biosynthesis.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0003824 catalytic activity | IEA GO_REF:0000002 | MODIFY | Summary: The generic catalytic-activity term should be replaced by the exact MoaA reaction. Reason: Per the RADICAL_SAM treatment rule, the generic catalytic-activity row is replaced by the specific reaction the gene already carries (GO:0061798, accepted below). Q88E69 is a HAMAP MF_01225 MoaA family member, and the HAMAP rule assigns it the GTP 3',8-cyclase reaction. Proposed replacements: GTP 3',8'-cyclase activity Supporting Evidence: file:PSEPK/moaA/moaA-uniprot.txt FUNCTION: Catalyzes the cyclization of GTP to (8S)-3',8-cyclo-7,8- dihydroguanosine 5'-triphosphate. file:PSEPK/moaA/moaA-uniprot.txt SIMILARITY: Belongs to the radical SAM superfamily. MoaA family. |
| GO:0005525 GTP binding | IEA GO_REF:0000104 | KEEP AS NON CORE | Summary: GTP binding is a valid substrate-binding property but is less informative than the catalytic term. Reason: GTP is the substrate of the MoaA reaction and the HAMAP GTP-binding residues are annotated on Q88E69; structurally, GTP binds the C-terminal [4Fe-4S] cluster in the S. aureus ortholog. Substrate binding is a component of the cyclase activity, so non-core, as in ECOLI/moaA. Supporting Evidence: file:PSEPK/moaA/moaA-uniprot.txt /ligand="GTP" PMID:16632608 MoaA binds 5'-GTP with high affinity and interacts through its C-terminal [4Fe-4S] cluster with the guanine N1 and N2 atoms |
| GO:0006777 Mo-molybdopterin cofactor biosynthetic process | IEA GO_REF:0000120 | ACCEPT | Summary: MoaA performs the first committed reaction of Mo-molybdopterin cofactor biosynthesis. Reason: MoaA performs a step of the process (GTP cyclization), and the HAMAP rule places Q88E69 in molybdopterin biosynthesis; same action as ECOLI/moaA. Supporting Evidence: file:PSEPK/moaA/moaA-uniprot.txt PATHWAY: Cofactor biosynthesis; molybdopterin biosynthesis. PMID:14761975 precursor Z purified from Escherichia coli overproducing MoaA and MoaC, two proteins essential for bacterial precursor Z synthesis |
| GO:0046872 metal ion binding | IEA GO_REF:0000002 | MODIFY | Summary: Generic metal-ion binding is compatible with the two iron-sulfur clusters but is non-core. Reason: Following the RADICAL_SAM project rule for the generic domain-derived rows (projects/RADICAL_SAM.md): a lateral correction. The record assigns both of MoaA's metal centres to [4Fe-4S] clusters and no mononuclear site, so GO:0051539 replaces the generic parent. ECOLI/moaA makes the same replacement. Proposed replacements: 4 iron, 4 sulfur cluster binding Supporting Evidence: file:PSEPK/moaA/moaA-uniprot.txt Name=[4Fe-4S] cluster; Xref=ChEBI:CHEBI:49883; |
| GO:0051536 iron-sulfur cluster binding | IEA GO_REF:0000002 | MODIFY | Summary: This broad iron-sulfur-cluster binding term is redundant with the more specific retained [4Fe-4S]-cluster binding annotation. Reason: Following the RADICAL_SAM project rule for the generic domain-derived rows (projects/RADICAL_SAM.md): correct but general, so MODIFY rather than MARK_AS_OVER_ANNOTATED: the protein does bind iron-sulfur clusters, two of them, both [4Fe-4S]. Proposed replacements: 4 iron, 4 sulfur cluster binding Supporting Evidence: file:PSEPK/moaA/moaA-uniprot.txt Note=Binds 2 [4Fe-4S] clusters. Binds 1 [4Fe-4S] cluster coordinated |
| GO:0051539 4 iron, 4 sulfur cluster binding | IEA GO_REF:0000120 | ACCEPT | Summary: The specific [4Fe-4S]-cluster binding annotation is supported but is not the catalytic function. Reason: Core cofactor binding: one cluster generates the 5'-deoxyadenosyl radical and the second binds the GTP-derived substrate, so GTP 3',8-cyclase activity is not separable from cluster binding. Catalysis is established, so ACCEPT rather than KEEP_AS_NON_CORE, as in ECOLI/moaA. Supporting Evidence: file:PSEPK/moaA/moaA-uniprot.txt Note=Binds 2 [4Fe-4S] clusters. Binds 1 [4Fe-4S] cluster coordinated |
| GO:0061798 GTP 3',8'-cyclase activity | IEA GO_REF:0000120 | ACCEPT | Summary: GTP 3',8'-cyclase activity is the exact core molecular function of canonical KT2440 MoaA. Reason: The reviewed entry supplies the exact reaction, Rhea:49576, and EC 4.1.99.22. Supporting Evidence: file:PSEPK/moaA/moaA-uniprot.txt CC -!- CATALYTIC ACTIVITY: CC Reaction=GTP + AH2 + S-adenosyl-L-methionine = (8S)-3',8-cyclo-7,8- CC dihydroguanosine 5'-triphosphate + 5'-deoxyadenosine + L-methionine + CC A + H(+); Xref=Rhea:RHEA:49576, ChEBI:CHEBI:13193, ChEBI:CHEBI:15378, CC ChEBI:CHEBI:17319, ChEBI:CHEBI:17499, ChEBI:CHEBI:37565, CC ChEBI:CHEBI:57844, ChEBI:CHEBI:59789, ChEBI:CHEBI:131766; CC EC=4.1.99.22; Evidence={ECO:0000255|HAMAP-Rule:MF_01225}; PMID:23627491 Instead, 3′,8-cH2GTP is transferred to MoaC where a complex rearrangement reaction proceeds. |
| GO:0061799 cyclic pyranopterin monophosphate synthase activity | IEA GO_REF:0000118 | REMOVE | Summary: Cyclic pyranopterin monophosphate synthase activity belongs to MoaC, not MoaA. Reason: MoaA makes the cyclic GTP intermediate 3',8-cH2GTP; the distinct MoaC enzyme converts that intermediate to cPMP, and MoaA itself lacks the residues for the rearrangement. KT2440 encodes a separate HAMAP MF_01224 MoaC. The TreeGrafter transfer comes from the PTHR22960 node that also holds bifunctional MOCS1 fusions, whose MoaC-like MOCS1B domain carries this activity; single-domain MoaA lacks it. Same action as ECOLI/moaA. Supporting Evidence: file:PSEPK/moaA/moaA-deep-research-openscientist.md MoaA is **not** the enzyme that forms the cyclic phosphate or releases pyrophosphate (that is MoaC) PMID:23627491 In contrast to GTP cyclohydrolases I, MoaA is incapable of catalyzing the rearrangement reactions, presumably due to the lack of appropriate amino acid residues in the active-site. PMID:23627491 Instead, 3′,8-cH2GTP is transferred to MoaC where a complex rearrangement reaction proceeds. file:PSEPK/moaC/moaC-uniprot.txt SIMILARITY: Belongs to the MoaC family. |
| GO:1904047 S-adenosyl-L-methionine binding | IEA GO_REF:0000104 | ACCEPT | Summary: SAM binding is a valid radical-SAM mechanistic property but is not the core catalytic annotation. Reason: The project rule ACCEPTs GO:1904047 for every active member: SAM is the cosubstrate that the enzyme itself binds and cleaves, which makes it a core molecular function rather than a peripheral one. ECOLI/moaA ACCEPTs the same row. Supporting Evidence: file:PSEPK/moaA/moaA-uniprot.txt cysteines and an exchangeable S-adenosyl-L-methionine |
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Download this section (compressed HTML)Q: Under which conditions, if any, do PP_2482 or PP_1969 contribute to the same cPMP-forming reaction as canonical moaA?
Experiment: Measure cPMP production and molybdoenzyme activity in single and combined moaA-family deletion strains, with complementation by each paralog.
Type: targeted genetics and metabolite profiling
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