mgtE (PA0913, Q9I544) notes

2026-10-28 review (PseudoCAP IBA-seed worklist, rank 20)

No deep-research provider was available; literature collected by PubMed search
and the cached abstracts. The PseudoCAP-cited paper (PMID:24722909, Coffey et
al. 2014) is abstract-only here: there is no PMC copy and the publisher page
and the thesis repository could not be fetched.

Identity and family

UniProt Q9I544 (unreviewed), 482 aa, "Magnesium transporter MgtE" by
RuleBase; SLC41A/MgtE family; N-terminal MgtE_N domain, two CBS domains,
C-terminal MgtE transmembrane domain (Pfam PF01769, NCBIfam TIGR00400 mgtE);
three predicted TM segments (393-415, 421-446, 458-481)
[file:PSEAE/mgtE/mgtE-uniprot.txt].
PANTHER PTHR43773:SF1. The PAINT node PTN000227060 is the family root (25
leaves, 21 organisms) [file:PSEAE/mgtE/mgtE-bioinformatics/RESULTS.md].

Function in P. aeruginosa

Inner-membrane Mg2+ transporter and virulence modulator
PMID:24722909.
Transport and cytotoxicity regulation were both demonstrated, and
Mg2+-binding sites in the connecting helix were required for coupling them
PMID:24722909. The sites were identified from a homology model built on the
T. thermophilus crystal structure PMID:24722909. As far as the abstract
shows, no direct Mg2+-binding assay was done.
mgtE mutation raises T3SS transcription and cytotoxicity; transport-defective
variants still complement the cytotoxicity phenotype PMID:20028803.
Mechanism of T3SS inhibition: mgtE expression acts through GacAS to raise
rsmY/rsmZ and inhibit exsA translation PMID:28847924. This is regulatory output, probably indirect;
no GO process for it is proposed here.
mgtE is not essential and is induced by low Mg2+ PMID:24722909.

Family reference: T. thermophilus MgtE (Q5SMG8)

Homodimer; Mg2+ in the pore at Asp432 and at cytosolic sensor sites
PMID:17700703.
Mg2+-selective channel gated by cytosolic Mg2+ PMID:19798051.
Mg2+-binding residues mapped onto PA0913: 8 of 15 positions identical
(including pore Asp -> Asp466) and 2 conservative
[file:PSEAE/mgtE/mgtE-bioinformatics/RESULTS.md].

Annotation decisions (summary)

GO:0015095 magnesium ion transmembrane transporter activity (IEA): ACCEPT, core.
GO:1903830 magnesium ion transmembrane transport (IEA): ACCEPT, core.
GO:0015693 magnesium ion transport (IBA, IEA, IMP): MODIFY to GO:1903830.
GO:0000287 magnesium ion binding (IBA, IMP): KEEP_AS_NON_CORE; true by
similarity to the Tth structure, but the IMP row is not binding evidence.
GO:0008324, GO:0006812, GO:0098655: MODIFY to the Mg2+-specific terms.
GO:0016020 membrane: MODIFY to GO:0005886; GO:0005886 (IEA): ACCEPT.

PseudoCAP IBA-seed assessment

PTN node	node term	n_seeds	leaf IBAs	seed annotation (term, evidence, PMID)	verdict	rationale
PTN000227060	GO:0015693 magnesium ion transport	1 (sole)	25	GO:0015693, IMP, PMID:24722909	SOUND	The abstract reports Mg2+ transport by P. aeruginosa MgtE, and transport-defective variants are described in PMID:20028803. A transporter's own process, not an indirect phenotype. Node placement issue: 6 of 22 resolved leaves (SCO5154, Rv1232c, CBO0203, TM_0892, A7T8Y4, VC_0300) lack the MgtE transmembrane domain (PF01769) yet inherit the IBA; NOT annotations are needed there.
PTN000227060	GO:0000287 magnesium ion binding	1 (sole)	25	GO:0000287, IMP, PMID:24722909	INDIRECT-PHENOTYPE	A mutant phenotype cannot show ion binding. Coffey et al. mutated Mg2+ sites predicted from the Tth homology model and saw lost coupling of functions. The binding claim is true by similarity (Tth Q5SMG8 crystal structures; ligands conserved in PA0913), but this seed is not experimental binding evidence. Q5SMG8 is in PTHR43773:SF1 but not a tree leaf, so it cannot re-seed the node; the IBD rests only on this row.

Term breadth: magnesium ion transport (and Mg2+ binding) at the eubacterial
family root suits the full-length MgtE transporters, which dominate the clade.
The six TM-less leaves are scattered losses (the Actinomycetales clade
PTN005181931, CBO0203, TM_0892, A7T8Y4, VC_0300) and need NOT rows rather
than a smaller node.