GbcB (PA5411) is the reductase component of the two-component Rieske-type glycine betaine monooxygenase of Pseudomonas aeruginosa, which demethylates glycine betaine to dimethylglycine in the catabolism of choline-derived quaternary amines. It has an N-terminal FAD- and NAD-binding reductase module and a C-terminal plant-type [2Fe-2S] ferredoxin domain, and is thought to pass electrons from NADH to the oxygenase subunit GbcA. gbcA and gbcB mutants cannot grow on glycine betaine but grow on dimethylglycine, and their expression is induced by glycine betaine through the AraC-family activator GbdR.
Definition: Catalysis of the reaction glycine betaine + NADH + O2 + H+ = N,N-dimethylglycine + formaldehyde + NAD+ + H2O (EC 1.14.13.251, RHEA:45700).
Justification: The two-component Rieske glycine betaine monooxygenase (GbcAB in Pseudomonas) has no GO term, so the reductase and oxygenase subunits can be annotated only to generic oxidoreductase activity.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0016491 oxidoreductase activity | IBA GO_REF:0000033 | ACCEPT | Summary: IBA from PTN005342051, seeded by E. coli Hcr (IDA), M. tuberculosis Hmp (IDA) and this gene's own PseudoCAP row (expected self-appearance). Sound at the node. Reason: True, and as specific as the evidence allows: GO has no glycine betaine monooxygenase term and the reductase's electron acceptor has not been assayed. Supporting Evidence: PMID:17951379 Subsequent nuclear magnetic resonance (NMR) experiments with 1,2-(13)C-labeled choline indicated that these genes are necessary for conversion of GB to DMG. |
| GO:0016491 oxidoreductase activity | IDA PMID:17951379 Identification of two gene clusters and a transcriptional re... | ACCEPT | Summary: PseudoCAP seed row for PTN005342051. The abstract shows gbcAB are needed for conversion of GB to DMG (mutant growth, in vivo 13C NMR). Seed verdict SOUND for the term; the evidence code is probably IMP rather than IDA. Reason: The term is correct for an FAD/NAD/2Fe-2S reductase required for the GB demethylation step. Supporting Evidence: PMID:17951379 Subsequent nuclear magnetic resonance (NMR) experiments with 1,2-(13)C-labeled choline indicated that these genes are necessary for conversion of GB to DMG. |
| GO:0016491 oxidoreductase activity | IEA GO_REF:0000120 | ACCEPT | Summary: Combined IEA from the FAD/NAD reductase domains. Reason: Consistent with the IBA and experimental rows. Supporting Evidence: PMID:17951379 Subsequent nuclear magnetic resonance (NMR) experiments with 1,2-(13)C-labeled choline indicated that these genes are necessary for conversion of GB to DMG. |
| GO:0031457 glycine betaine catabolic process | IMP PMID:17951379 Identification of two gene clusters and a transcriptional re... | ACCEPT | Summary: PseudoCAP row. gbcB mutants cannot grow on GB but grow on DMG, and cannot convert GB to DMG. Reason: GbcB is a subunit of the enzyme that performs the first demethylation of GB, so it does part of the work of the process; core. Supporting Evidence: PMID:17951379 strains with mutations in two genes, gbcA (PA5410) and gbcB (PA5411), were capable of growth on dimethylglycine (DMG), a catabolic product of GB, but not on GB itself |
| GO:0051536 iron-sulfur cluster binding | IEA GO_REF:0000002 | TOO GENERAL | Summary: InterPro2GO from the 2Fe-2S ferredoxin domain. Reason: Entailed by the accepted GO:0051537 2 iron, 2 sulfur cluster binding. |
| GO:0051537 2 iron, 2 sulfur cluster binding | IEA GO_REF:0000002 | ACCEPT | Summary: InterPro2GO from the 2Fe-2S ferredoxin cysteine signature; UniProt marks four cysteine cluster ligands. Reason: The plant-type ferredoxin domain and conserved ligands support the cluster. Supporting Evidence: file:PSEAE/gbcB/gbcB-uniprot.txt /ligand="[2Fe-2S] cluster" |
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Download this section (compressed HTML)Q: Does purified GbcB reduce GbcA directly with NADH, and is its activity specific to GbcA or shared with other Rieske oxygenases?
Experiment: Reconstitute GbcA and GbcB in vitro, measure NADH-dependent GB to DMG conversion and NADH oxidation by GbcB alone with cytochrome c or GbcA as acceptor.
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