PA4156

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.

Summary: Cell outer membrane from the UniProt subcellular location and family rule.

Reason: Consistent with the IBA row; a TonB-dependent receptor barrel.

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. Current UniProt places PA4156 in PANTHER PTHR32552 rather than PTHR30069; the IBA follows the PANTHER version used by PAINT, and the function is supported on this gene by its own mutant either way.

Summary: PseudoCAP IMP seed for the IBD at PTN004738955. A pyoverdine- and pyochelin-deficient strain also lacking fvbA cannot use vibriobactin as an iron source.

Reason: Seed verdict SOUND. Loss of vibriobactin-dependent iron acquisition when the TonB-dependent receptor gene is inactivated, for a close homologue of the V. cholerae vibriobactin receptor ViuA, is direct genetic evidence that FvbA transports ferric vibriobactin across the outer membrane.

Summary: PseudoCAP IMP; fvbA mutant cannot use vibriobactin.

Reason: True but entailed by GO:0044718 siderophore transmembrane transport, accepted on this gene (is_a descendant).

Summary: Siderophore-iron import into cell, inferred by GO from the molecular function row.

Reason: The mutant phenotype is failure to acquire iron from vibriobactin, i.e. siderophore-mediated iron import.

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.

Summary: CollecTF annotation of the Fur target gene fvbA to cellular response to iron ion, from evidence that Fur regulates fvbA.

Reason: The evidence is that fvbA expression is controlled by Fur (and by vibriobactin and FvbR), which makes the gene a Fur target, not a participant in the iron response; the abstract calls these analyses preliminary. Iron-regulated expression of a target gene is not by itself a role in responding to iron. Fur itself carries the response term.