vgrG1b (PA0095, Q9I737) notes

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

Fetched with just fetch-gene PSEAE Q9I737 --alias vgrG1b; accession matches the
worklist (reviewed entry VGR1B_PSEAE). No deep-research provider key was
available. PMID:21325275 and PMID:24794869 read in full; PMID:30455305 is
abstract only (fetched with just fetch-pmid), but its abstract states the
decisive facts.

Identity and literature

741 aa VgrG-family protein, encoded in HSI-I near vgrG1a and closely related
to it (64% identity, PMID:21325275 Fig. 2).
Its own release is independent of all three T6SSs
PMID:21325275,
and it is dispensable for the H1-T6SS
PMID:21325275.
The authors excluded lysis and periplasmic leakage as the cause of its
appearance in supernatants.
It nevertheless carries its own cargo: reintroducing vgrG1b alone into a
triple vgrG1abc mutant restores activity
PMID:24794869,
with the partner protein encoded in its own cluster
PMID:24794869.
The 2018 work establishes the spike role and the H1-T6SS dependence of that
delivery PMID:30455305; the same
abstract states that the delivery of Tse7 is dependent on the H1-T6SS cluster.

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?
PTN002088178	GO:0033103 protein secretion by the type VI secretion system	3 (Q9I737, Q9I741, Q9I0F3)	13 (3 taxa)	GO:0033103, IMP, PMID:21325275 (PseudoCAP)	WRONG	The cited paper's vgrG1b result is negative on both counts (the mutant secretes Hcp1 and the other VgrGs normally; its own release needs no ClpV). An IMP row cannot rest on that. The term itself is true of vgrG1b on later evidence (PMID:30455305, PMID:24794869), so the fix is the reference, not the term. Full text read, so CONFIRMED.	vgrG1a (Q9I741) and vgrG1c (Q9I0F3), both SOUND (IDA PMID:20114026, IMP PMID:21325275)	Yes — the node rests on the vgrG1a and vgrG1c seeds, so no GO_CENTRAL defect
PTN002088178	GO:0033104 type VI protein secretion system complex	3 (Q9I737, Q9I0F3, Q9I741)	13 (3 taxa)	GO:0033104, IMP, PMID:21325275 (PseudoCAP)	WRONG	Same reference problem. Complex membership is defensible for a spike protein whose cargo delivery needs the H1-T6SS cluster, but not core: the Hcp1 apparatus assembles and fires without VgrG1b.	as above	Yes

One PSEUDOCAP defect (WRONG_REFERENCE, REPOINT PMID:21325275 ->
PMID:30455305, CONFIRMED) is recorded on the GO:0033103 IMP row and covers both
rows. No GO_CENTRAL defect: the node term suits the clade (13 leaves, all VgrG
spike proteins in three taxa) and the IBDs survive without this seed.

Decisions summary

ACCEPT: GO:0033103 (IBA, IEA, IMP) — term true, reference wrong on the IMP row.
KEEP_AS_NON_CORE: GO:0033104 (IBA, IEA, IMP); extracellular region (EXP, IEA).
Counts: ACCEPT 3, KEEP_AS_NON_CORE 5.
Defects: PSEUDOCAP 1 (WRONG_REFERENCE, CONFIRMED), GO_CENTRAL 0.
One BIOLOGY knowledge gap recorded: the export route for VgrG1b itself is
unidentified.