FpvR (PA2388) is the FecR-family transmembrane anti-sigma factor of the ferri-pyoverdine cell-surface signalling system of Pseudomonas aeruginosa. It spans the cytoplasmic membrane once, with a cytoplasmic N-terminal region (FecR_N, DUF4880) and a periplasmic FecR domain that receives the signal from the TonB-dependent receptor FpvA when ferri-pyoverdine binds. Its cytoplasmic region binds and inhibits two ECF sigma factors, PvdS, which directs transcription of pyoverdine synthesis and virulence genes (exotoxin A, PrpL), and FpvI, which directs transcription of the receptor gene fpvA; the FpvI interaction involves sigma region 4. Ferri-pyoverdine signalling relieves this inhibition, so FpvR couples siderophore availability to the production of pyoverdine and of its receptor.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0016989 sigma factor antagonist activity | IMP PMID:12492864 Siderophore-mediated cell signalling in Pseudomonas aerugino... | ACCEPT | Summary: PseudoCAP IMP and a seed of the PTN001250434 IBD. The abstract states that FpvR negatively regulates FpvI activity, and that ferri-pyoverdine signalling through FpvR controls PvdS. Direct binding and inhibition of both sigma factors by the cytoplasmic region of FpvR was shown later. Reason: Core function; the seed is sound. fpvR has the FecR_N/FecR domain architecture of cell-surface-signalling anti-sigma factors. Supporting Evidence: PMID:25433393 The cytoplasmic region of FpvR bound to and inhibited both FpvI and PvdS when the proteins were co-expressed in Escherichia coli. PMID:12492864 FpvR negatively regulates the activity of a second ECF sigma factor, FpvI, which is required for the synthesis of FpvA |
| GO:0045892 negative regulation of DNA-templated transcription | IEA GO_REF:0000108 | MODIFY | Summary: Logical inference from the sigma factor antagonist activity. Sequestering an ECF sigma factor prevents it from directing RNA polymerase to its promoters, so the process is negative regulation of transcription initiation. Reason: Correct but general. GO:2000143 negative regulation of DNA-templated transcription initiation (is_a GO:0045892) is the precise process for an anti-sigma factor, and matches the GO:2000142 accepted on the cognate sigma factor reviews. Proposed replacements: negative regulation of DNA-templated transcription initiation Supporting Evidence: PMID:25433393 The cytoplasmic region of FpvR bound to and inhibited both FpvI and PvdS when the proteins were co-expressed in Escherichia coli. PMID:12492864 FpvR negatively regulates the activity of a second ECF sigma factor, FpvI, which is required for the synthesis of FpvA |
| GO:1900705 negative regulation of siderophore biosynthetic process | IMP PMID:12492864 Siderophore-mediated cell signalling in Pseudomonas aerugino... | KEEP AS NON CORE | Summary: FpvR inhibits PvdS, the sigma factor required for transcription of the pyoverdine synthesis genes, so it negatively regulates pyoverdine biosynthesis. It acts on transcription of the biosynthetic genes, which is a legitimate route of regulation of the process. Reason: True regulatory consequence of the antagonist activity on PvdS; non-core relative to the molecular function. Supporting Evidence: PMID:25433393 FpvI and PvdS are required for expression of the ferri-pyoverdine receptor gene fpvA and of pyoverdine synthesis genes respectively. PMID:25433393 The cytoplasmic region of FpvR bound to and inhibited both FpvI and PvdS when the proteins were co-expressed in Escherichia coli. |
| GO:0005886 plasma membrane | IC PMID:25433393 Interactions between an anti-sigma protein and two sigma fac... | NEW | Summary: Proposed location. The protein has a single Phobius transmembrane helix between the cytoplasmic FecR_N region and the periplasmic FecR domain, and the literature describes it as a transmembrane (cytoplasmic membrane) anti-sigma factor that relays a periplasmic signal to a cytoplasmic sigma factor. Reason: Two independent lines agree (predicted TM helix with the FecR domain architecture, and the published description); no cellular component is annotated at present. Supporting Evidence: PMID:25433393 In the absence of pyoverdine the anti-sigma factor FpvR that spans the cytoplasmic membrane inhibits the activities of both FpvI and PvdS |
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Download this section (compressed HTML)Q: FecR-family proteins act both as anti-sigma factors and, through their cytoplasmic N-terminal fragments, as pro-sigma factors. Should the pro-sigma (sigma factor activation) role be captured in GO, and which term would describe it?
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