pilN (PA5043, G3XD30) notes

Identity

UniProt G3XD30 (PILN_PSEAE), reviewed, 198 aa, gene pilN, locus PA5043.
Single TM segment 19-39 (ECO:0000255), short cytoplasmic N-terminal tail,
periplasmic coiled-coil + ferredoxin-like domain. Pfam PF05137 PilN,
PANTHER PTHR40278:SF2 (type IV pilus inner membrane component PilN).
Second gene of the pilMNOPQ operon PMID:7565110.

Mutants lack functional fimbriae: transposon screen for loss of twitching;
complementation; phage sensitivity; EM [PMID:7565110 "PilM-P were found to be
required for fimbrial biogenesis by complementation studies using twitching
motility and sensitivity to fimbrial-specific phage as indicators of the
presence of functional fimbriae."; "This was confirmed by electron
microscopy."]. PilN predicted inner-membrane PMID:7565110 and resembles the T2SS GspL protein XpsL.
Inner membrane location, PilMNOP complex PMID:19857645; interdependent stability PMID:19857645. UniProt: "Cell inner membrane {ECO:0000269|PubMed:19857645}";
"Deletion mutants lack surface pili."
Periplasmic PilN/PilO heterodimer PMID:19857646.
PilN cytoplasmic tail binds PilM; PilNOP links to PilQ via PilP
PMID:23457250; conserved N-terminal residues needed for
twitching, phage sensitivity and surface PilA PMID:23457250.
PilN binding monomerises PilM and alters its ATP site PMID:27022027.
PilN/PilO homo- and heterodimers in vivo; some locked configurations abolish
twitching PMID:27474743.

PAINT IBD.gaf (cached .cache/paint): IBDs at PTN002220336 for GO:0043107
and GO:0043683 (2017-02-28), and GO:0044096 type IV pilus and GO:0005886
plasma membrane (2026-06-17), all WITH UniProtKB:G3XD30 only.
Leaves (paint_uniprot GAF): G3XD30 (P. aeruginosa), Q4W563 (Neisseria
meningitidis NMB1809 PilN), Q74BL0 (Geobacter GSU2031 PilN), Q74C93
(Geobacter GSU1781, named "PulN" but PilN family, PTHR40278:SF2), Q8EK24
(Shewanella), Q8P5V4 (Xanthomonas), Q9KNU7 (Vibrio VC_2633). 7 leaves, 6
taxa, all PilN subfamily members per UniProt PANTHER xref. Node scope is
appropriate.
The GO:0044096 and GO:0005886 IBAs are not yet in the GOA file for pilN
(fetched 2026-10-28; QuickGO shows only GO:0043107 and GO:0043683 IBAs from
this node), so there is no IBA type IV pilus row to review. The GO_CENTRAL
defect for the type IV pilus IBD is recorded on the PseudoCAP seed row.

PseudoCAP IBA-seed assessment

PTN node	node term	n_seeds	leaf IBAs	seed annotation (term, evidence, PMID)	verdict	rationale
PTN002220336	GO:0044096 type IV pilus	1 (sole)	7 (6 taxa)	GO:0044096 type IV pilus, located_in, IMP, PMID:7565110 (PseudoCAP)	INDIRECT-PHENOTYPE	"Mutant has no pili" recorded as a location. PilN is a bitopic inner-membrane alignment-subcomplex protein, not part of the surface fibre GO:0044096 defines. The IBD (added 2026-06-17) has no other support.
PTN002220336	GO:0043107 type IV pilus-dependent motility	1 (sole)	7 (6 taxa)	GO:0043107, IMP, PMID:7565110 and PMID:19857645 (PseudoCAP)	SOUND	PilN is a structural component of the pilus machine; mutants and N-terminal point mutants abolish twitching. Node confined to PilN orthologues.
PTN002220336	GO:0043683 type IV pilus assembly	1 (sole)	7 (6 taxa)	GO:0043683, IMP, PMID:7565110 and PMID:19857645 (PseudoCAP)	SOUND	Deletion mutants lack surface pili; PilN anchors the PilMNOP alignment subcomplex that is required for assembly. Conserved across the PilN clade.

ACCEPT: plasma membrane (EXP, IEA); motility (IBA, IMP x2); assembly (IBA,
IMP x2).
REMOVE: located_in type IV pilus (IMP, PseudoCAP), with PSEUDOCAP and
GO_CENTRAL defects.