pilU (PA0396, UniProt G3XCX3) review notes

No deep-research provider was available; the notes below are from my own
reading of the cached publications, PubMed and the UniProt entry.

Identity

Fetched accession G3XCX3 (PILU_PSEAE), PA0396, 382 aa, matches the
PseudoCAP worklist entry (rank 39).
PilT/PilU family (InterPro IPR006321, NCBIfam TIGR01420 pilT_fam), PANTHER
PTHR30486:SF12 "TYPE IV PILUS ATPASE PILU"; Walker A ATP site 133-138 by
similarity [file:PSEAE/pilU/pilU-uniprot.txt]. No nuclease domain.

pilU lies directly downstream of pilT; mutants lose twitching, are
hyperfimbriate but stay phage-sensitive [PMID:7854122 "The other three
transposon mutations were found to have occurred within a new gene located
directly downstream of pilT."; "Like pilT mutants, the pilU mutants were
hyperfimbriate"].
Purified PilU is an ATPase PMID:18174131.
Unipolar localization at the piliated pole PMID:15659660.
PilT-dependent retraction ATPase PMID:31525185.
PilU matters for retraction under load PMID:30804544.
Crystal structure: hexameric motor PMID:41055394; pilU mutants have high cAMP and some
PilA/PilY1 alleles restore twitching without PilU.
Species variation: P. stutzeri pilU is dispensable for twitching
PMID:11466271;
D. nodosus pilU is required PMID:18310333.

PTN node	node term	n_seeds	leaf IBAs	seed annotation (term, evidence, PMID)	verdict	rationale
PTN000766390	GO:0016888 DNA endonuclease activity, producing 5'-phosphomonoesters	1 (sole seed)	13 (9 taxa)	GO:0016888, IDA, PMID:18174131 (PseudoCAP)	WRONG	The paper (correct PMID) assays ATPase activity of purified PilU; no nuclease assay, no nuclease domain. GO:0016888 is a mis-keyed id for the adjacent GO:0016887 ATP hydrolysis activity, which PseudoCAP gave PilB from the same paper. The IBD and its ~13 leaf IBAs (including the one back onto PilU) should be withdrawn or repointed to ATP hydrolysis activity.
PTN000766390	GO:0043107 type IV pilus-dependent motility	1 (sole seed)	13 (9 taxa)	GO:0043107, IMP, PMID:7854122 (PseudoCAP)	SOUND	pilU transposon mutants lose twitching while keeping (excess) pili; PilU is itself a retraction motor, so it does part of the work of twitching. Suitable for a small PilU clade, with the caveat that some orthologs (P. stutzeri; Neisseria) are not needed for twitching.

ACCEPT: ATP binding (IEA), cytoplasm (EXP, IEA), type IV pilus-dependent
motility (IBA, IMP).
MODIFY: DNA endonuclease activity IDA -> ATP hydrolysis activity
(GO:0016887); PseudoCAP WRONG_TERM defect.
REMOVE: DNA endonuclease activity IBA (propagated keying error); GO_Central
WRONG_TERM defect on PTN000766390.
No GO process term exists for type IV pilus retraction; raised as a
suggested question.