mexT (PA2492, Q9I0Z0) notes
Sources read on 2026-11-05: UniProt Q9I0Z0 (MEXT_PSEAE), the GOA file, cached abstracts
of PMID:9044268, PMID:10515918, PMID:20727012, and cached full texts of PMID:21075931,
PMID:19846594, PMID:31722511, PMID:39708318, PMID:41128522. PMID:31859619 (PAO1 subline
mexT variability) is cited by UniProt but not cached and was not read. No deep-research
provider file (no keys). LysR comparators already reviewed: genes/PSEAE/ampR, trpI
(different PAINT node, PTN000794521).
Biology
- MexT is a LysR-type activator encoded upstream of mexEF-oprN; nfxC-type mutants
overexpress the pump
PMID:10515918;
MexT also activates qrh (mexS)
PMID:10515918.
- Purified MexT binds the mexT-proximal nod box of the mexE promoter
PMID:20727012;
DNase I footprinting finds two sites
PMID:31722511.
- MexT directly activates a regulon of ~12 genes with a conserved motif, independent of
MexEF-OprN PMID:19846594.
- Full-length MexT is a homotetramer (SEC-MALS), RD a dimer
PMID:31722511.
- Indirect/pleiotropic roles: in PAO1, mexT (with mexS) represses T3SS (ExoS secretion),
elastase and pyocyanin (PMID:21075931, full text); loss of MexT raises aminoglycoside
and colistin resistance and virulence (PMID:39708318); MexT shapes the QS hierarchy,
mostly through MexEF-OprN export of quinolones
PMID:41128522.
Annotation judgements (summary)
- Core: GO:0001216 activator activity, GO:0000976 cis-regulatory region binding,
GO:0045893 positive regulation of transcription (ACCEPT on all experimental and IBA
rows).
- GO:0003700, GO:0006355: TOO_GENERAL (entailed by GO:0001216 / GO:0045893).
- GO:0001217 repressor activity (UniProt IMP, PMID:41128522): the full text attributes
pqs repression to MexEF-OprN, not to MexT binding the pqs promoter. MARK_AS_OVER_ANNOTATED.
- GO:0045892 negative regulation of transcription (same paper): KEEP_AS_NON_CORE (true in
the indirect sense).
- GO:0045861 negative regulation of proteolysis (PseudoCAP, PMID:21075931): rests on more
elastase in the mutant. MexT is a transcription factor; it does not act on proteolysis.
REMOVE with PSEUDOCAP WRONG_TERM (CONFIRMED, full text read).
- GO:0050709 negative regulation of protein secretion (PseudoCAP): mexT mutant secretes
more ExoS; MexT represses T3SS through MexS. KEEP_AS_NON_CORE.
- GO:1900377 negative regulation of secondary metabolite biosynthetic process (PseudoCAP):
pyocyanin; MODIFY to GO:1900981 negative regulation of phenazine biosynthetic process
(no negative pyocyanine-regulation term exists).
- GO:0046677 response to antibiotic: resistance phenotypes, not a response.
MARK_AS_OVER_ANNOTATED.
- GO:0009372 quorum sensing, GO:0010629 negative regulation of gene expression:
KEEP_AS_NON_CORE.
PseudoCAP IBA-seed assessment
Other seeds' experimental support queried live in QuickGO on 2026-11-05.
| PTN node |
node term |
n_seeds |
leaf IBAs |
seed annotation (term, evidence, PMID) |
verdict |
rationale |
other seeds |
IBD stands without this seed? |
| PTN001248361 |
GO:0006355 regulation of DNA-templated transcription |
3 |
46 (9 taxa) |
GO:0045893, IMP, PMID:10515918 (PseudoCAP) |
SOUND |
Abstract: mexE::lacZ and qrh::lacZ are activated by MexT. Direct binding shown later (PMID:20727012, PMID:31722511). |
E. coli LeuO P10151 (EcoCyc IMP GO:0006355, PMID:9422614), S. Typhimurium LeuO P46924 (CollecTF IPI/IEP GO:0000976, GO:0001216, GO:0045893, PMID:22149171); MexT also has CollecTF and UniProt rows |
Yes; both LeuO seeds have experimental support |
The node term is generic and suits a 9-taxon clade of LysR regulators. No PSEUDOCAP
defect on the seed row and no GO_CENTRAL defect on PTN001248361. The node's other IBDs
(GO:0001216, GO:0000976, GO:0032993) are seeded by MexT and S. Typhimurium LeuO and are
also sound. ampR and trpI sit on PTN000794521, not this node.
Defects recorded: PSEUDOCAP WRONG_TERM on GO:0045861 (CONFIRMED). GO:1900377 is a
refinement (MODIFY to GO:1900981), not an error, so no defect.