ChtA (PA4675) is a TonB-dependent outer-membrane receptor of Pseudomonas aeruginosa PAO1 for the citrate-hydroxamate xenosiderophores aerobactin, rhizobactin 1021 and schizokinen. It has the 22-strand beta-barrel and N-terminal plug domain of the TonB-dependent receptor family and imports the iron-loaded siderophores across the outer membrane using energy supplied by the TonB1 system. Unlike many other P. aeruginosa xenosiderophore pathways, use of these three siderophores depends on ChtA alone. chtA is preceded by a Fur box and is repressed by Fur under iron-replete conditions.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0009279 cell outer membrane | IBA GO_REF:0000033 | ACCEPT | Summary: Cell outer membrane from PAINT node PTN002824128, seeded by E. coli TonB-dependent receptors with direct localization (FepA P05825, BtuB P06129, CirA P17315 and YncD P76115). Reason: TonB-dependent receptors are 22-strand outer-membrane beta-barrels with an N-terminal plug; the family membership and the cleavable signal peptide agree with outer-membrane location. Supporting Evidence: file:PSEAE/PA4675/PA4675-uniprot.txt PF00593; TonB_dep_Rec_b-barrel file:PSEAE/PA4675/PA4675-uniprot.txt FT SIGNAL 1..28 |
| GO:0009279 cell outer membrane | IEA GO_REF:0000120 | ACCEPT | Summary: Cell outer membrane from the UniProt subcellular location and family rule. Reason: Consistent with the IBA row; a TonB-dependent receptor barrel. Supporting Evidence: file:PSEAE/PA4675/PA4675-uniprot.txt PF00593; TonB_dep_Rec_b-barrel |
| GO:0015343 siderophore-iron transmembrane transporter activity | IEA GO_REF:0000002 | TOO GENERAL | Summary: InterPro2GO siderophore-iron transmembrane transporter activity. Reason: True but entailed by GO:0015344 siderophore uptake transmembrane transporter activity, accepted on this gene (is_a descendant of GO:0015343). Supporting Evidence: PMID:16549659 The chtA and PA1365 genes were mutated by insertional inactivation and it was demonstrated that ChtA is the outer-membrane receptor for aerobactin. |
| GO:0015344 siderophore uptake transmembrane transporter activity | IBA GO_REF:0000033 | ACCEPT | Summary: Siderophore uptake transmembrane transporter activity from PAINT node PTN004738955 (PTHR30069 TonB-dependent siderophore receptor clade, 142 leaves in 21 taxa). Its four IBD seeds are the PAO1 receptors PfeA, ChtA (PA4675), FvbA (PA4156) and PirA, each through a PseudoCAP IMP row; the node is assessed in the PA4675 notes. Reason: Core function. The gene product is itself a seed of this IBD through an experimental row on its own ferric-siderophore uptake, which is expected, not circular; the node is grounded in four independently characterized PAO1 receptors and sits within a TonB-dependent siderophore receptor clade where ferric-siderophore uptake is the established function. Supporting Evidence: PMID:16549659 The chtA and PA1365 genes were mutated by insertional inactivation and it was demonstrated that ChtA is the outer-membrane receptor for aerobactin. PMID:16549659 The utilization of citrate hydroxamate siderophores by P. aeruginosa was demonstrated to be TonB1 dependent. |
| GO:0015344 siderophore uptake transmembrane transporter activity | IMP PMID:16549659 Identification and characterization of an iron-regulated gen... | ACCEPT | Summary: PseudoCAP IMP seed for the IBD at PTN004738955. The chtA insertion mutant cannot use aerobactin, rhizobactin 1021 or schizokinen, with no redundancy from other receptors, and utilization is TonB1-dependent. Reason: Seed verdict SOUND. For an outer-membrane TonB-dependent receptor, loss of use of specific ferric siderophores in a single mutant, without redundancy, is direct genetic evidence that the receptor transports those ferric siderophores; the abstract calls ChtA the outer-membrane receptor for aerobactin. Supporting Evidence: PMID:16549659 The chtA and PA1365 genes were mutated by insertional inactivation and it was demonstrated that ChtA is the outer-membrane receptor for aerobactin. PMID:16549659 ChtA also mediated the utilization of rhizobactin 1021 and schizokinen, which are structurally similar to aerobactin. PMID:16549659 there was no apparent redundancy in the utilization of aerobactin, rhizobactin 1021 and schizokinen PMID:16549659 The utilization of citrate hydroxamate siderophores by P. aeruginosa was demonstrated to be TonB1 dependent. |
| GO:0015891 siderophore transport | IEA GO_REF:0000002 | TOO GENERAL | Summary: InterPro2GO siderophore transport. Reason: True but entailed by GO:0044718 siderophore transmembrane transport, accepted on this gene (is_a descendant). Supporting Evidence: PMID:16549659 The chtA and PA1365 genes were mutated by insertional inactivation and it was demonstrated that ChtA is the outer-membrane receptor for aerobactin. |
| GO:0015891 siderophore transport | IMP PMID:16549659 Identification and characterization of an iron-regulated gen... | TOO GENERAL | Summary: PseudoCAP IMP; chtA mutant cannot use aerobactin, rhizobactin 1021 or schizokinen. Reason: True but entailed by GO:0044718 siderophore transmembrane transport, accepted on this gene (is_a descendant). Supporting Evidence: PMID:16549659 The chtA and PA1365 genes were mutated by insertional inactivation and it was demonstrated that ChtA is the outer-membrane receptor for aerobactin. PMID:16549659 ChtA also mediated the utilization of rhizobactin 1021 and schizokinen, which are structurally similar to aerobactin. |
| GO:0033214 siderophore-iron import into cell | IEA GO_REF:0000120 | ACCEPT | Summary: Siderophore-iron import into cell, inferred from the molecular function rows. Reason: ChtA supports growth on iron supplied as ferric citrate-hydroxamate siderophores, i.e. siderophore-mediated iron acquisition; with three distinct siderophores this broad term is appropriate. Supporting Evidence: PMID:16549659 The chtA and PA1365 genes were mutated by insertional inactivation and it was demonstrated that ChtA is the outer-membrane receptor for aerobactin. PMID:16549659 ChtA also mediated the utilization of rhizobactin 1021 and schizokinen, which are structurally similar to aerobactin. |
| GO:0038023 signaling receptor activity | IEA GO_REF:0000002 | REMOVE | Summary: InterPro2GO signaling receptor activity from the TonB-dependent siderophore receptor signature. Reason: The mapping is wrong for this member. Signalling TonB-dependent receptors (transducers such as FpvA or FecA) carry an N-terminal signalling extension of about 70 residues before the plug, which contacts an anti-sigma factor in the periplasm; this protein has only a signal peptide followed directly by the plug domain, so it is a receptor-transporter, not a signalling receptor. Same decision as for PfeA. Supporting Evidence: file:PSEAE/PA4675/PA4675-uniprot.txt FT SIGNAL 1..28 file:PSEAE/PA4675/PA4675-uniprot.txt PF07715; Plug |
| GO:0044718 siderophore transmembrane transport | IBA GO_REF:0000033 | ACCEPT | Summary: Siderophore transmembrane transport from PAINT node PTN004738955, seeded by E. coli CirA (P17315, IMP). Reason: Core process; TonB-dependent ferric-siderophore uptake across the outer membrane, shown for this receptor by its mutant phenotype. Supporting Evidence: PMID:16549659 The chtA and PA1365 genes were mutated by insertional inactivation and it was demonstrated that ChtA is the outer-membrane receptor for aerobactin. PMID:16549659 The utilization of citrate hydroxamate siderophores by P. aeruginosa was demonstrated to be TonB1 dependent. |
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Download this section (compressed HTML)Q: GO:0015344 siderophore uptake transmembrane transporter activity is defined by a proton-coupled ferrioxamine symport reaction (TC 2.A.1.16), yet it is the standard term for TonB-dependent outer-membrane receptors. Should GO provide a TonB-dependent siderophore receptor activity term or broaden the definition?
Experiment: Measure 55Fe-aerobactin uptake and aerobactin binding by purified ChtA, to add biochemical evidence to the genetic data.
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