pilA (PA4525, P04739) notes

Identity

UniProt P04739 (PILA_PSEAE), reviewed, 149 aa, type IVa major pilin.
6-residue leader cleaved by PilD and N-methylated on Phe7; N-terminal
hydrophobic helix (residues 7-27, membrane-spanning before assembly);
C-terminal globular domain with the 134-147 disulfide loop. Pfam PF00114
Pilin, PF07963 N_methyl; PANTHER PTHR30093:SF34.

Literature

Fibre structure: cryo-EM of the native PAO1 pilus PMID:39666767; the globular domain coats
the fibre surface PMID:39666767.
Inner-membrane pool regulates its own transcription via PilS PMID:27162347.
pilA mutant (strain PAK) lacks pili and twitching; reduced association with
and invasion of corneal epithelial cells PMID:12933890.
Attachment: SPR shows pilA mutants are defective in attachment
PMID:16849183.
Biofilm caps formed by pilus-driven migration PMID:14507363.
Host Ca2+ signalling via CAMLG: yeast two-hybrid and over-expression of pilA
inside BEAS-2B cells PMID:23266901.
Host ER membrane location (UniProt EXP) comes from this paper; it reflects
heterologous expression of PilA inside host cells, not a demonstrated
delivery route during infection.
PMID:2985436 (Pasloske et al. 1985) cloned and sequenced the strain PAK
pilin gene; abstract-only, says nothing about location assay. PAK pilin is a
different-strain orthologue (both group II pilins). The location claim is
nevertheless certain for PAO1 PilA (PMID:39666767).
PMID:9224878 (Alm and Mattick 1997, Gene) reads, from its abstract, as a
review of type 4 fimbrial genes PMID:9224878. The full text (supplied by the user, read 2026-11-05)
is largely an overview, but its Fig. 1 is a twitching assay of the PAK wild
type and a pilA mutant, so the PseudoCAP IMP is supported. The suspected
evidence-code defect (2026-10-29 audit) was removed.
PMID:25049409 (Chung et al. 2014, Tip phage protein inhibits PilB): CACAO
rows for cell surface and cytosol. Full text not available via PMC tool
(PMC4128137 returned no body). Surface PilA (sheared pili) is fine; the
cytosol row is odd because unassembled pilin is an inner-membrane protein.

PANTHER node PTN002013003

IBDs of GO:0043107 and GO:0044096 (2019-08-22), WITH UniProtKB:P04739 only.
Two sub-nodes (PTN004739243, PTN004739244) carry NOT IRDs for both terms
(2026-03-04), so PAINT curators have already pruned divergent branches.
Remaining leaves (10, 9 taxa): P. aeruginosa PilA, E. coli K-12 PpdD
(P36647), H. influenzae PpdD homologue (P44623), Salmonella (Q7CR79),
Yersinia (A0A5P8YC84), Coxiella (Q83EZ7), Shewanella PilA (Q8EJP5),
Xanthomonas PilE and XCC3098, Vibrio VC_2423. All PTHR30093:SF34 major
pilins. The location claim (major pilin of a type IV pilus) fits the clade.
Motility is less certain for leaves from species without documented
twitching (E. coli K-12 PpdD is cryptic; H. influenzae is non-motile, its
pili mediate competence/adherence), but the seed itself is sound.

PseudoCAP IBA-seed assessment

PTN node	node term	n_seeds	leaf IBAs	seed annotation (term, evidence, PMID)	verdict	rationale
PTN002013003	GO:0043107 type IV pilus-dependent motility	1 (sole)	10 (9 taxa)	GO:0043107, IDA, PMID:12933890; GO:0043107, IMP, PMID:9224878 (PseudoCAP)	SOUND	PilA is the fibre subunit whose extension/retraction drives twitching; pilA mutants are non-piliated and non-twitching. Evidence codes are off (12933890 is a mutant assay, so IMP, checked in the full text; 9224878 is an overview but its Fig. 1 is a pilA mutant twitching assay, so its IMP stands), the 12933890 code recorded as a PSEUDOCAP defect; the claim stands. Motility at the node is a mild over-reach for PpdD of E. coli K-12 and H. influenzae, which do not twitch.
PTN002013003	GO:0044096 type IV pilus	1 (sole)	10 (9 taxa)	GO:0044096, IDA, PMID:2985436 (PseudoCAP)	SOUND	PilA is the major structural subunit of the fibre (cryo-EM, PMID:39666767). The cited paper is a strain PAK gene-sequencing paper whose abstract shows no location assay, so the reference is weak, but the claim is correct and appropriate for a clade of major pilins.

Decisions summary

ACCEPT: plasma membrane (EXP, IEA); cell adhesion (IEA); motility (IBA,
IDA, IMP); type IV pilus (IBA, IDA).
MODIFY to GO:0044096 type IV pilus: pilus (EXP, IDA, IEA); cell surface
(IDA).
KEEP_AS_NON_CORE: biofilm attachment (IMP 16849183), biofilm formation on
inanimate substrate (IMP 14507363).
MARK_AS_OVER_ANNOTATED: host cell ER membrane (EXP, IEA); regulation of
calcium-mediated signaling (IMP).
UNDECIDED: cytosol (IDA, CACAO, full text unavailable).