pirA (PA0931, Q9I527) notes

Review session 2026-11-05 (PseudoCAP IBA-seed protocol, tier 2)

Fetched with just fetch-gene PSEAE Q9I527 --alias pirA (accession fetch). Accession Q9I527
(Swiss-Prot) matches the worklist. No deep-research keys; literature from cached seed/other
papers (PMID:15899402, PMID:28137795, PMID:33350053, all abstract-only) and the UniProt
record.

Identity

TonB-dependent outer-membrane receptor, 742 aa + signal peptide 1-28. Plug 57-184,
beta-barrel 189-742, TonB box motif 725-742. InterPro PirA/FepA/PfeA family (IPR058134);
PTHR30069:SF8. Crystal structure 5FP2. No N-terminal signalling extension, so a
receptor-transporter.

Literature

Second ferric-enterobactin receptor, redundant with PfeA
PMID:15899402;
PMID:15899402;
PMID:15899402.
Imports catecholamine-chelated iron (l-DOPA, norepinephrine preference)
PMID:33350053;
PMID:33350053.
Entry route for siderophore-monobactam conjugates; structure solved
PMID:28137795.

Annotation decisions

Cell outer membrane (IBA, IEA): ACCEPT. Siderophore uptake transmembrane transporter
activity (IBA, IEA, IMP): ACCEPT core. Enterobactin transport (IMP) and enterobactin
transmembrane transporter activity (IEA, IMP): ACCEPT core. Siderophore-iron import into
cell (IEA): ACCEPT.
Siderophore-iron transmembrane transporter activity (IEA, GO:0015343): TOO_GENERAL
(GO:0015344 is_a descendant). Siderophore transport (IEA x1 + IMP x3, GO:0015891):
TOO_GENERAL (GO:0044718 is_a descendant). Iron ion transport (IMP, GO:0006826):
TOO_GENERAL (GO:0033214 is_a descendant).
Signaling receptor activity (IEA, GO:0038023): REMOVE (InterPro2GO over-mapping; no
signalling extension, as for PfeA and ChtA).
Action counts: ACCEPT 10, TOO_GENERAL 6, REMOVE 1. Defects: none (PseudoCAP seed sound;
signaling row is an InterPro2GO electronic over-mapping removed, not a source defect).
Note: the GO:0015344 IMP seed rests on pfeA pirA double-mutant data with single-mutant
controls (PfeA/PirA are redundant for enterobactin); this is a genetic-interaction
phenotype but, with the controls, still identifies PirA as a ferric-enterobactin receptor.
GO:0042931 could be refined to GO:0015620 ferric-enterobactin transmembrane transporter
activity to name the iron-loaded ligand, as noted for PfeA; left as-is (acceptable parent).

PseudoCAP IBA-seed assessment

PTN node	node term	n_seeds	leaf IBAs	seed annotation (term, evidence, PMID)	verdict	rationale	other seeds	IBD stands without this seed?
PTN004738955	GO:0015344 siderophore uptake transmembrane transporter activity	4	142 (21 taxa)	GO:0015344, IMP, PMID:15899402	SOUND	pfeA pirA double mutant, not either single mutant, fails to use ferric enterobactin and catecholate analogues; PirA confirmed as a second ferric-enterobactin receptor. Later: catecholamine-iron uptake, crystal structure.	PfeA (Q05098), ChtA (PA4675, Q9HVC0), FvbA (PA4156, Q9HWM5) — PseudoCAP IMP; E. coli CirA (P17315) at the partner process IBD	Yes

The node-level assessment of PTN004738955 is recorded once in PA4675-notes.md (IBD sound,
node term suits the clade, no GO_CENTRAL defect). pirA is consistent with it.