mexA (PA0425, P52477) notes

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

Fetched with just fetch-gene PSEAE P52477 --alias mexA; accession matches the
worklist. Reviewed Swiss-Prot entry. No deep-research provider was used. Cached
papers: PMID:33009415, PMID:30944318 and PMID:11114896 have full text;
PMID:8540696 (the PseudoCAP seed paper), PMID:25901994, PMID:9973347 and
PMID:15226509 are abstract-only (the PMC copy of PMID:8540696 returned no text).
The PubMed MCP search returned API errors.

Literature

MexA is the inner-membrane-anchored periplasmic adaptor of MexAB-OprM; six MexA
molecules join the MexB trimer to the OprM trimer
PMID:30944318.
MexA is required for MexB proton-coupled transport in proteoliposomes
PMID:33009415,
and the reconstituted pump transports substrate
PMID:25901994.
Seed paper: null mutants accumulate more drug and are more susceptible
PMID:8540696.
Efflux of the quorum-sensing signal 3OC12-HSL
PMID:9973347.

Decisions

ACCEPT: plasma membrane (IBA, IEA); antiporter activity (contributes_to, IDA);
efflux transmembrane transporter activity (IBA, IDA x2, IMP); cell envelope (IDA);
xenobiotic export from cell (IDA); GO:0140330 (IBA, IDA); efflux pump complex
(IDA x3).
KEEP_AS_NON_CORE: response to antibiotic (IBA; PseudoCAP IDA with evidence-code
defect); identical protein binding and protein homooligomerization (IMP; MexA
hexamer).
TOO_GENERAL: membrane (IEA); transmembrane transporter activity (IEA);
transmembrane transport (IDA, IMP, IEA).
Counts: ACCEPT 14, KEEP_AS_NON_CORE 4, TOO_GENERAL 5.

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?
PTN001249140	GO:0046677 response to antibiotic	6	38 (12 taxa)	GO:0046677, IDA, PMID:8540696 (PseudoCAP)	SOUND	Abstract: mexA null mutants accumulate more tetracycline, norfloxacin and benzylpenicillin and are more susceptible to beta-lactams. The term is right; the experiments are on null and overproducing mutants, so the code should be IMP (PSEUDOCAP WRONG_EVIDENCE_CODE, PROBABLE: abstract only).	E. coli AcrA (P0AE06; EcoCyc IMP/IGI), E. coli MdtE (P37636; EcoCyc IMP), MexE (Q9I0Y9; IGI), MexC (G3XD25; IGI), MexX (G3XD21; PseudoCAP EXP/IMP)	Yes

No GO_CENTRAL defect. The node-level assessment (clade of RND-pump membrane fusion
proteins, term suitable, IBD supported by several independent seeds) is recorded
once on mexX: genes/PSEAE/mexX/mexX-notes.md. MexA is also the seed of the
PTN001249140 GO:0140330 IBD (with AcrA and AcrE), supported here by UniProt IDA
(PMID:25901994).