RhdA (PA4956) is the principal rhodanese (thiosulfate:cyanide sulfurtransferase, EC 2.8.1.1) of the cyanogenic bacterium Pseudomonas aeruginosa. It is a two-domain rhodanese that transfers the outer sulfur of thiosulfate to cyanide through a persulfide on the conserved catalytic Cys230, producing the less toxic thiocyanate and sulfite. RhdA is cytoplasmic, accounts for about 90% of cytoplasmic rhodanese activity, and is expressed constitutively from two promoters in an operon with PA4955 and psd. A deletion mutant grows poorly under cyanogenic conditions and is outcompeted by wild type, so RhdA helps protect P. aeruginosa against its own (endogenous) cyanide.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0004792 thiosulfate-cyanide sulfurtransferase activity | EXP PMID:15522204 Characterization of a rhodanese from the cyanogenic bacteriu... | ACCEPT | Summary: UniProt EXP from the biochemical characterisation of recombinant RhdA (kinetics for thiosulfate and cyanide, persulfide on Cys230). Reason: Direct enzymology on the purified recombinant protein. Supporting Evidence: PMID:15522204 the biochemical characterization of recombinant P. aeruginosa rhodanese (Pa RhdA), catalyzing the sulfur transfer from thiosulfate to a thiophilic acceptor, e.g., cyanide, is reported. |
| GO:0004792 thiosulfate-cyanide sulfurtransferase activity | IEA GO_REF:0000120 | ACCEPT | Summary: EC 2.8.1.1 / RHEA:16881 mapping of the curated catalytic activity. Reason: Consistent with the direct evidence. Supporting Evidence: file:PSEAE/rhdA/rhdA-uniprot.txt Catalyzes the sulfur transfer reaction from thiosulfate to cyanide, thus converting cyanide to the less toxic thiocyanate |
| GO:0004792 thiosulfate-cyanide sulfurtransferase activity | IMP PMID:17098912 Involvement of Pseudomonas aeruginosa rhodanese in protectio... | ACCEPT | Summary: PseudoCAP IMP. Cytoplasmic rhodanese activity of the PAO1 deletion mutant fell to 12% of wild type and was restored by complementation, with RhdA protein absent from mutant cytoplasm. Reason: Full text read. The mutant and complementation data show that RhdA carries most of the cell's cytoplasmic rhodanese activity; with the recombinant-enzyme data this is sound IMP support for the activity. This is the PTN000146159 seed row; verdict SOUND. Supporting Evidence: PMID:17098912 remarkable differences were observed at the cytoplasmic level, with PAO1Ξ rhdA showing 12% of wild-type activity |
| GO:0005737 cytoplasm | EXP PMID:17098912 Involvement of Pseudomonas aeruginosa rhodanese in protectio... | ACCEPT | Summary: UniProt EXP from cell fractionation with marker enzymes and immunoblotting. Reason: Fractions were checked with isocitrate dehydrogenase and beta-lactamase markers; RhdA was immunodetected only in the cytoplasmic fraction. Supporting Evidence: PMID:17098912 Cell fractionation unambiguously localized RhdA in the cytoplasm, where it accounts for ca. 90% of total rhodanese activity. |
| GO:0005737 cytoplasm | IEA GO_REF:0000044 | ACCEPT | Summary: Cytoplasm from the UniProt subcellular-location mapping. Reason: Consistent with the fractionation data. Supporting Evidence: PMID:17098912 RhdA is a cytoplasmic enzyme acting as the principal rhodanese in P. aeruginosa. |
| GO:0016783 sulfurtransferase activity | IBA GO_REF:0000033 | TOO GENERAL | Summary: IBA sulfurtransferase activity from PTN000146159 (10 seeds in the IBD.gaf record, 44 leaf IBAs), a broad rhodanese/3-mercaptopyruvate sulfurtransferase clade seeded by bovine TST, E. coli SseA and YnjE, rodent and zebrafish MPST, yeast, Arabidopsis and RhdA itself. Reason: True, and the broad node term is the right choice for a clade that mixes thiosulfate and 3-mercaptopyruvate sulfurtransferases. For RhdA it is entailed by GO:0004792 thiosulfate-cyanide sulfurtransferase activity (is_a descendant), accepted above on direct evidence. |
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Download this section (compressed HTML)Q: Is cyanide the physiological sulfur acceptor of RhdA in vivo, or does RhdA mainly supply persulfide sulfur to other acceptors (for example thioredoxin or iron-sulfur cluster assembly), with cyanide detoxification as a secondary role?
Experiment: Persulfide-trapping proteomics with a Cys230 substrate-trap RhdA variant in PAO1 under cyanogenic and non-cyanogenic growth to identify in vivo sulfur acceptors.
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