PA2057 (Q9I258) is an uncharacterised TonB-dependent outer membrane receptor of Pseudomonas aeruginosa PAO1 (PANTHER PTHR47234:SF1). The annotated 846-residue model lacks a signal peptide because it starts at an internal GTG codon; the PAO1 genome continues the reading frame 139 codons upstream to an ATG, adding a signal-peptide-like segment and an N-terminal extension (see gene_model_issues). The full-length protein is a TonB-dependent receptor of 985 residues. Receptors of this family bind a ligand at the cell surface and, energised by the TonB-ExbB-ExbD complex through the TonB box, translocate it across the outer membrane; many import siderophore-iron complexes or other scarce nutrients. The substrate of this receptor is not known.
The protein sequence of this entry may not correspond to a single real gene product (for example, two neighbouring genes joined into one model, or a truncated model). Read the name, features and annotations of the entry with this in mind.
WRONG START SITE CONFIRMED GENOMIC SEQUENCEORTHOLOG COMPARISONDOMAIN ARCHITECTURE
The PAO1 model (AAG05445.1, NP_250747.1; 846 aa) starts at an internal GTG that corresponds to the VVTGS motif of the receptor, so the entry has no signal peptide, which an outer-membrane beta-barrel protein must have. Translation of the PAO1 genome upstream of the annotated start continues the same open frame for 185 codons; from the ATG aligned with the start of the longer orthologous models it encodes 139 residues (MPHHAPSTRL...) beginning with a hydrophobic signal-peptide-like segment and followed by a segment resembling the STN domain of TonB-dependent transducers (not formally scanned). This extension is 137/139 identical to the N-terminus of a 985-aa P. aeruginosa variant (UniParc UPI000EB53B2E) in the same UniRef90 cluster, the commonest length in that cluster (98 of 336 members). Functional statements here apply to the full-length 985-residue protein. The truncation does not affect the outer-membrane location.
Supported by:
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0009279 cell outer membrane | IEA GO_REF:0000120 | ACCEPT | Summary: UniProt subcellular location from the TonB-dependent receptor family rule. Reason: The plug and 22-strand TonB-dependent receptor beta-barrel domains define an integral outer-membrane protein of a Gram-negative bacterium; cell outer membrane is the precise term. Supporting Evidence: file:PSEAE/PA2057/PA2057-uniprot.txt PF00593; TonB_dep_Rec_b-barrel; 1. file:PSEAE/PA2057/PA2057-uniprot.txt SIMILARITY: Belongs to the TonB-dependent receptor family. |
| GO:0019867 outer membrane | IBA GO_REF:0000033 | TOO GENERAL | Summary: IBA from the PTN002933024 IBD (22 leaves in P. aeruginosa, Shewanella and Xanthomonas), seeded by four PAO1 receptors including PA2057 itself (expected, not circular), all from the PseudoCAP IDA citing PMID:18086184. Reason: True but entailed: GO:0009279 cell outer membrane, accepted in this review, is_a GO:0019867. The node term suits the clade, whose leaves are all TonB-dependent receptors (BtuB, BfeA and relatives), although its four seeds rest on one abstract-only paper; the node-level assessment is in the PA2590 notes. Supporting Evidence: file:PSEAE/PA2057/PA2057-uniprot.txt PF00593; TonB_dep_Rec_b-barrel; 1. |
| GO:0019867 outer membrane | IDA PMID:18086184 Characterization of five novel Pseudomonas aeruginosa cell-s... | TOO GENERAL | Summary: PseudoCAP IDA; seed of the PTN002933024 IBD. Seed verdict UNVERIFIABLE (abstract only), but the location is correct on sequence grounds. Reason: The outer-membrane location is right for a TonB-dependent receptor, but GO:0009279 cell outer membrane, accepted in this review, is_a GO:0019867. Whether this paper detected PA2057 in an outer-membrane fraction could not be checked from the abstract, so no defect is recorded. Supporting Evidence: PMID:18086184 This regulatory system consists of an outer membrane-localized TonB-dependent receptor (TonB-dependent transducer) file:PSEAE/PA2057/PA2057-uniprot.txt PF00593; TonB_dep_Rec_b-barrel; 1. |
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Download this section (compressed HTML)Experiment: Screen siderophores and other TonB-dependent substrates for growth promotion under iron limitation in a PA2057 deletion mutant versus wild type and complemented strain, and confirm outer-membrane localisation by fractionation of a tagged protein.
What is not known — curated, literature-grounded statements of the open unknowns (the inverse of core functions).
Gap: The ligand imported or sensed by PA2057 is unknown, as is which ECF sigma factor controls it and whether it signals to an anti-sigma factor.
BIOLOGY
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