PA1057 encodes subunit E (ShaE/MrpE) of the Sha (Mrp/Mnh/Pha) multisubunit Na+/H+ antiporter of Pseudomonas aeruginosa PAO1. It is a 174-residue integral membrane protein with short predicted transmembrane helices and a cytoplasmic region, in the CPA3 subunit E (MNHE) family. It is the fourth gene of the six-gene sha cluster PA1054-PA1059, in which shaA and shaB are fused. The cluster restores Na+ tolerance and Na+/H+ antiport to an E. coli strain lacking its major antiporters, and in P. aeruginosa the Sha antiporter is largely responsible for Na+ extrusion and supports virulence in mouse infection models. In Bacillus Mrp antiporters, subunit E is needed for normal levels of the other subunits and for assembly of the active hetero-oligomeric complex, though one species reports it dispensable for transport. Structures place it at the dimer interface, and it has been proposed as the cytoplasmic entry route for Na+.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0005886 plasma membrane | IEA GO_REF:0000044 | ACCEPT | Summary: Subcellular location mapping (cell membrane, multi-pass). PA1057 has predicted TM helices and is a subunit of an inner-membrane Na+/H+ antiporter complex. Reason: Correct location for a subunit of the Na+-extruding membrane complex. Supporting Evidence: file:PSEAE/PA1057/PA1057-uniprot.txt TRANSMEM 12..30 PMID:16030218 genes PA1054 to PA1059 encode a Na+/H+ antiporter that is largely responsible for Na+ extrusion in P. aeruginosa |
| GO:0006812 monoatomic cation transport | IEA GO_REF:0000002 | MODIFY | Summary: InterPro2GO from the cation antiporter subunit E family. Correct but general. Reason: True but general; GO:0035725 sodium ion transmembrane transport (a descendant, already on this gene) is the supported process. Proposed replacements: sodium ion transmembrane transport Supporting Evidence: PMID:16030218 genes PA1054 to PA1059 encode a Na+/H+ antiporter that is largely responsible for Na+ extrusion in P. aeruginosa |
| GO:0008324 monoatomic cation transmembrane transporter activity | IEA GO_REF:0000002 | MODIFY | Summary: InterPro2GO from the cation antiporter subunit E family. Correct but general. Reason: True but general; GO:0015385 sodium:proton antiporter activity (a descendant, already on this gene) is the supported activity, to which this subunit contributes as part of the complex. Proposed replacements: sodium:proton antiporter activity Supporting Evidence: PMID:16030218 The gene cluster PA1054 to PA1059, but not the cluster with a deletion of PA1054, complemented a growth defect in the presence of 0.2 M NaCl and a defect in Na+/H+ antiport activity of the Escherichia coli TO114 mutant lacking the three major Na+/H+ antiporters |
| GO:0015385 sodium:proton antiporter activity | IBA GO_REF:0000033 | ACCEPT | Summary: IBA from PTN002160407, the LUCA root of PTHR34584 (Mrp/Mnh subunit E family, 20 reference leaves), sole-seeded by the PseudoCAP IMP row for this gene. PA1057 is ShaE of the Sha antiporter. The activity belongs to the hetero-oligomeric complex, and MrpE is an accessory subunit needed for assembly. The node also covers MBH/MBX hydrogenase subunit A proteins (TK2080, TK1226). Reason: The core activity of the complex this protein belongs to; kept, with the qualifier corrected to contributes_to (GO_CENTRAL defect). Propagation Review Root cause: SOURCE WEAK OR INFERRED Sources checked: PANTHER:PTN002160407 · PTN002160407 SUPPORTS TRANSFER Family-root IBD; right for Mrp/Mnh/Pha subunit E as a contribution to complex activity. It reaches MBH/MBX hydrogenase subunits, where a Na+/H+ antiporter MF is doubtful. UniProtKB:Q9I4R7 · PA1057 (shaE) SOURCE WEAK OR INFERRED Sole seed; PseudoCAP IMP, but the PMID:16030218 abstract reports a disruption of PA1054 only. Supporting Evidence: PMID:16030218 The gene cluster PA1054 to PA1059, but not the cluster with a deletion of PA1054, complemented a growth defect in the presence of 0.2 M NaCl and a defect in Na+/H+ antiport activity of the Escherichia coli TO114 mutant lacking the three major Na+/H+ antiporters PMID:20624916 The results extended indications that MrpE is required for normal membrane levels of other Mrp proteins and for complex formation. file:PSEAE/PA1057/PA1057-bioinformatics/RESULTS.md PTN002160407 is the root of the PTHR34584 tree (LUCA speciation node, is_family_root: True): 20 leaves in 17 organisms. |
| GO:0015385 sodium:proton antiporter activity | IMP PMID:16030218 Characterization of a multigene-encoded sodium/hydrogen anti... | ACCEPT | Summary: PseudoCAP IMP, the sole seed of the PTN002160407 antiporter IBD. The paper shows antiport for the whole PA1054-PA1059 cluster, lost when PA1054 is deleted, and reports a P. aeruginosa disruption of PA1054 only. The abstract describes no PA1057 mutant, and the full text (read 2026-11-05) confirms none was made, so a mutant-phenotype code is wrong for PA1057. PA1057 is a subunit of the antiporter complex. Reason: PA1057 is part of the Na+/H+ antiporter, so the claim is kept as the core activity. It is a contribution (contributes_to), and the evidence is cluster-level, with no PA1057 mutant in the paper (full text checked). Both are flagged to PseudoCAP. Supporting Evidence: PMID:16030218 The gene cluster PA1054 to PA1059, but not the cluster with a deletion of PA1054, complemented a growth defect in the presence of 0.2 M NaCl and a defect in Na+/H+ antiport activity of the Escherichia coli TO114 mutant lacking the three major Na+/H+ antiporters PMID:20624916 Antiport activity requires hetero-oligomeric complexes of all six or seven hydrophobic Mrp proteins (MrpA-MrpG). |
| GO:0016020 membrane | IEA GO_REF:0000002 | MODIFY | Summary: Generic membrane location from the family mapping. Reason: True but general; GO:0005886 plasma membrane (already on this gene) is the supported location. Proposed replacements: plasma membrane Supporting Evidence: file:PSEAE/PA1057/PA1057-uniprot.txt TRANSMEM 12..30 |
| GO:0035725 sodium ion transmembrane transport | IBA GO_REF:0000033 | ACCEPT | Summary: IBA from PTN002160407 (subunit E family root), sole-seeded by the PseudoCAP IMP row. Subunit E of Mrp-type complexes, including the Mrp-like module of archaeal MBH, takes part in Na+ translocation. The term suits the clade. Reason: Core process of the Sha complex in which this subunit participates; MrpE has been proposed as the cytoplasmic Na+ entry route. Propagation Review Root cause: NO FAILURE CORE Sources checked: PANTHER:PTN002160407 · PTN002160407 SUPPORTS TRANSFER Na+ transmembrane transport fits Mrp antiporter subunits and the Na+-translocating modules of MBH-type complexes. UniProtKB:Q9I4R7 · PA1057 (shaE) SOURCE WEAK OR INFERRED Sole seed; process supported by cluster-level evidence, but the IMP code looks wrong for PA1057. Supporting Evidence: PMID:16030218 genes PA1054 to PA1059 encode a Na+/H+ antiporter that is largely responsible for Na+ extrusion in P. aeruginosa PMID:36241630 while sodium is taken up from the cytoplasm by MrpE and released to the periplasm at the interface of MrpA, MrpC, and MrpD PMID:29754813 The Na+-translocating unit, absent in complex I, resembles that found in the Mrp H+/Na+ antiporter |
| GO:0035725 sodium ion transmembrane transport | IMP PMID:16030218 Characterization of a multigene-encoded sodium/hydrogen anti... | ACCEPT | Summary: PseudoCAP IMP, the sole seed of the PTN002160407 Na+ transport IBD. The Sha cluster is responsible for Na+ efflux, and PA1057 is one of its subunits. The IMP code looks wrong for PA1057 (no PA1057 mutant in the abstract). Reason: Process correct for this subunit of the Na+-extruding complex; evidence code flagged. Supporting Evidence: PMID:16030218 genes PA1054 to PA1059 encode a Na+/H+ antiporter that is largely responsible for Na+ extrusion in P. aeruginosa |
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Download this section (compressed HTML)Q: Should GO provide a cellular component term for the Mrp-type multisubunit Na+/H+ antiporter complex, by analogy with GO:1903103 potassium:proton antiporter complex, so that accessory subunits such as MrpE can be annotated to the complex?
Q: Is P. aeruginosa ShaE required for Sha antiport activity, as in B. pseudofirmus, or dispensable, as reported for B. subtilis?
Experiment: Make an in-frame PA1057 (shaE) deletion, then test Na+ tolerance, Na+ efflux and Sha complex assembly (BN-PAGE). Also express the cluster lacking only PA1057 in E. coli TO114 and assay Na+/H+ antiport in everted vesicles.
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