dsbB1 (PA5256) encodes one of the two DsbB-family disulfide bond formation proteins of Pseudomonas aeruginosa, a 163-residue inner-membrane protein with four transmembrane helices and two periplasmic cysteine pairs. Like E. coli DsbB it reoxidises the periplasmic thiol oxidase DsbA, passing the electrons to membrane quinones, so that DsbA can keep introducing disulfide bonds into envelope and secreted proteins. Its PA14 ortholog (PA14_69400) was named PaDsbB2 by Arts et al. 2013, opposite to the UniProt PAO1 numbering. PaDsbB2 and its paralog both reoxidise DsbA1 in vivo and in a quinone-containing in vitro reconstitution, with similar affinity for DsbA1, and are redundant - only the double mutant loses oxidative folding of pili, flagella and exoproteins such as elastase, and virulence.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0005886 plasma membrane | IEA GO_REF:0000120 | ACCEPT | Summary: Subcellular location mapping (cell inner membrane, multi-pass). Reason: Four TM helices with periplasmic loops carrying the catalytic cysteine pairs; DsbB acts in the cytoplasmic membrane, where it reaches the quinone pool. Supporting Evidence: PMID:24327342 These cysteine residues are required for EcDsbB activity: they shuttle the electrons away from EcDsbA and deliver them to bound quinone molecules. |
| GO:0006457 protein folding | IBA GO_REF:0000033 | ACCEPT | Summary: IBA from PTN002195183 (DsbB clade, 11 leaf IBAs in 8 taxa); its only two GO:0006457 seeds are the two P. aeruginosa DsbB paralogs, both by PseudoCAP IMP to PMID:24327342. Reason: DsbB performs a step of oxidative folding (regenerating oxidised DsbA), and the double mutant fails to fold disulfide-containing envelope proteins. Both seeds are sound and the clade is DsbB proteins, so the IBD stands; the self-seed is expected. Propagation Review Root cause: NO FAILURE CORE Sources checked: PANTHER:PTN002195183 · PTN002195183 SUPPORTS TRANSFER DsbB clade; oxidative protein folding is the conserved role of DsbB. UniProtKB:P21482 · dsbB1 (PA5256) (self) SUPPORTS TRANSFER PseudoCAP IMP PMID:24327342 (full text read). UniProtKB:P57701 · dsbB2 (PA0538) SUPPORTS TRANSFER PseudoCAP IMP PMID:24327342 (full text read). Supporting Evidence: PMID:24327342 Altogether, these data lead to the conclusion that both PaDsbB1 and PaDsbB2 participate in the folding of several virulence factors of P. aeruginosa |
| GO:0006457 protein folding | IEA GO_REF:0000002 | ACCEPT | Summary: InterPro2GO from the DsbB/BdbC family signature. Reason: Correct, as for the IBA and IMP rows. Supporting Evidence: PMID:24327342 Altogether, these data lead to the conclusion that both PaDsbB1 and PaDsbB2 participate in the folding of several virulence factors of P. aeruginosa |
| GO:0006457 protein folding | IMP PMID:24327342 Dissecting the machinery that introduces disulfide bonds in ... | ACCEPT | Summary: PseudoCAP seed row. Arts et al. 2013 (full text) - the dsbB1 dsbB2 double mutant (PA14) leaves DsbA1 reduced and fails to fold type IV pili, flagella, elastase and other exoproteins; each single gene complements. Purified enzymes reoxidise DsbA1 in vitro. Reason: Seed verdict SOUND. The phenotype is shown only in the double mutant, but complementation by either single gene and the in vitro reconstitution attribute the activity to each paralog. Supporting Evidence: PMID:24327342 the double PadsbB1B2 mutant being complemented by expression of either individual PadsbB1 or PadsbB2 gene PMID:24327342 These results indicate that both PaDsbB1 and PaDsbB2 control the redox state of PaDsbA1 and that both proteins are able to compensate for each other. |
| GO:0009055 electron transfer activity | IEA GO_REF:0000104 | MODIFY | Summary: UniRule generic electron transfer term. Reason: True in the sense that DsbB passes electrons from DsbA to quinone, but the enzyme reaction is known; GO:0016672 (sulfur group donor, quinone acceptor), the term E. coli DsbB carries by IDA, states it. Proposed replacements: oxidoreductase activity, acting on a sulfur group of donors, quinone or similar compound as acceptor Supporting Evidence: PMID:24327342 The reaction was performed in the presence of quinones (decylubiquinone). |
| GO:0015035 protein-disulfide reductase activity | IBA GO_REF:0000033 | ACCEPT | Summary: IBA from PTN002195183, seeded by E. coli DsbB (P0A6M2, IMP PMID:8430071). Reason: DsbB is the thiol-disulfide oxidoreductase that oxidises DsbA; the P. aeruginosa paralogs reoxidise DsbA1 with Michaelis-Menten kinetics. Propagation Review Root cause: NO FAILURE CORE Sources checked: PANTHER:PTN002195183 · PTN002195183 SUPPORTS TRANSFER DsbB clade. UniProtKB:P0A6M2 · E. coli DsbB SUPPORTS TRANSFER IMP seed (EcoCyc); also IDA for GO:0016672 (PMID:10428033). Supporting Evidence: PMID:24327342 Thus, PaDsbB1 and PaDsbB2 have similar affinities for PaDsbA1. |
| GO:0015035 protein-disulfide reductase activity | IEA GO_REF:0000120 | ACCEPT | Summary: Combined automated annotation from the DsbB family. Reason: Correct, as for the IBA row. Supporting Evidence: PMID:24327342 Thus, PaDsbB1 and PaDsbB2 have similar affinities for PaDsbA1. |
| GO:0016020 membrane | IEA GO_REF:0000002 | TOO GENERAL | Summary: InterPro2GO generic membrane. Reason: Entailed by GO:0005886 plasma membrane (is_a membrane), accepted above. |
| GO:0016672 oxidoreductase activity, acting on a sulfur group of donors, quinone or similar compound as acceptor | IDA PMID:24327342 Dissecting the machinery that introduces disulfide bonds in ... | NEW | Summary: Proposed. Partially purified PaDsbB2 (the PA14 ortholog of this gene, PA14_69400, identical in sequence) reoxidised reduced DsbA1 in the presence of decylubiquinone, with a Km of 9.0 uM for DsbA1. Reason: Direct in vitro evidence for the DsbB reaction (protein dithiol oxidised, quinone reduced); same term as E. coli DsbB IDA. Supporting Evidence: PMID:24327342 We calculated a Km of 8.1 µM PaDsbA1 for PaDsbB1 and 9.0 µM for PaDsbB2. PMID:24327342 The reaction was performed in the presence of quinones (decylubiquinone). |
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Download this section (compressed HTML)Q: UniProt names PAO1 PA5256 dsbB1 and PA0538 dsbB2, but the PA14 entries and Arts et al. 2013 use the opposite assignment (PaDsbB1 is PA14_07000, the PA0538 ortholog). Should the PAO1 gene names be aligned with the literature?
Experiment: Measure dsbB1 and dsbB2 expression across oxygen levels and in biofilms, and test whether either paralog prefers ubiquinone or menaquinone, to find conditions in which the two are not redundant.
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