PA5498 encodes ZnuA, the periplasmic solute-binding protein (cluster A-I, solute-binding protein family 9) of the ZnuABC ATP-binding cassette zinc importer of Pseudomonas aeruginosa. It has a Sec signal peptide and binds Zn2+ with nanomolar affinity (KD about 23 nM, roughly 1.6 Zn2+ per protein) and high selectivity, delivering it to the ZnuB permease for ATP-driven (ZnuC) uptake across the inner membrane. A znuA deletion lowers cellular zinc by about 60% without changing other metals, and znuABC mutants grow poorly under zinc limitation. znuA is repressed by zinc through the Fur-family regulator Zur (Np20, PA5499), whose gene lies in the adjacent zur-znuC-znuB operon.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0000006 high-affinity zinc transmembrane transporter activity | ISS PMID:9680209 The ZnuABC high-affinity zinc uptake system and its regulato... | MODIFY | Summary: PseudoCAP ISS to E. coli ZnuA for high-affinity zinc transmembrane transporter activity. Reason: ZnuA is the periplasmic binding protein of the ZnuABC importer: it binds Zn2+ and hands it to ZnuB, but does not itself move zinc across a membrane. The transmembrane transporter activity belongs to the ZnuABC complex, so the appropriate term is ABC-type zinc transporter activity (GO:0015633) with a contributes_to qualifier. Proposed replacements: ABC-type zinc transporter activity Supporting Evidence: PMID:26290475 The Znu permease comprises the solute-binding protein (SBP) ZnuA, and an ABC transporter, which consists of ZnuB PMID:26290475 titration with increasing concentrations of ZnuA revealed a KD for Zn2+ of 22.6 ± 6.4 nM |
| GO:0006829 zinc ion transport | IBA GO_REF:0000033 | TOO GENERAL | Summary: IBA from the PTN000767207 IBD, seeded by E. coli ZnuA (P39172) and this gene. Reason: The claim is sound (the node term suits a ZnuA clade, and both seeds have direct evidence), but zinc ion transmembrane transport (GO:0071577), accepted here, is_a zinc ion transport. Supporting Evidence: PMID:26290475 Metal accumulation analyses revealed a significant 59.6% decrease in cellular Zn2+ due to loss of the SBP |
| GO:0006829 zinc ion transport | IEA GO_REF:0000002 | TOO GENERAL | Summary: InterPro2GO zinc ion transport from the ZnuA domain. Reason: Zinc ion transmembrane transport (GO:0071577), accepted here, is_a zinc ion transport. |
| GO:0006829 zinc ion transport | IMP PMID:26290475 ZnuA and zinc homeostasis in Pseudomonas aeruginosa. | TOO GENERAL | Summary: PseudoCAP IMP and one of the two seeds of the PTN000767207 IBD. Full text: whole-cell ICP-MS of Delta-znuA shows a 59.6% drop in cellular zinc with other metals unaffected; purified ZnuA binds zinc with nanomolar affinity. Reason: Sound seed: the solute-binding protein is a working part of the importer, so loss of zinc uptake reflects its own role. The term is entailed by zinc ion transmembrane transport (GO:0071577), accepted here. Supporting Evidence: PMID:26290475 Metal accumulation analyses revealed a significant 59.6% decrease in cellular Zn2+ due to loss of the SBP |
| GO:0008270 zinc ion binding | IDA PMID:26290475 ZnuA and zinc homeostasis in Pseudomonas aeruginosa. | ACCEPT | Summary: PseudoCAP IDA. Apo-ZnuA binds Zn2+ with KD 22.6 nM and about 1.6 Zn2+ per protein; zinc gives the largest thermal stabilisation. Reason: Direct binding measurement on purified protein; the core molecular activity of the binding protein. Supporting Evidence: PMID:26290475 titration with increasing concentrations of ZnuA revealed a KD for Zn2+ of 22.6 ± 6.4 nM |
| GO:0010043 response to zinc ion | IMP PMID:24086521 The transcriptional regulator Np20 is the zinc uptake regula... | MARK AS OVER ANNOTATED | Summary: PseudoCAP IMP response to zinc ion. In the cited paper the znuA data are slower growth of the deletion mutant in zinc-depleted medium. Reason: Poor growth when zinc is scarce is the expected consequence of losing zinc uptake, not a cellular response to zinc carried out by ZnuA. The zinc-responsive control of znuA is performed by Zur. Supporting Evidence: PMID:24086521 the inability to express the putative znuA, znuB, or znuC genes resulted in decreased growth at 18 hours |
| GO:0030001 metal ion transport | IEA GO_REF:0000002 | TOO GENERAL | Summary: Metal ion transport from InterPro. Reason: Entailed by zinc ion transmembrane transport (GO:0071577), accepted here. |
| GO:0042597 periplasmic space | IEA GO_REF:0000044 | ACCEPT | Summary: Periplasmic space from UniProt subcellular location mapping. Reason: Sec signal peptide (SignalP) and the solute-binding-protein role place ZnuA in the periplasm. Supporting Evidence: file:PSEAE/PA5498/PA5498-uniprot.txt SIGNAL 1..24 PMID:26290475 The Znu permease comprises the solute-binding protein (SBP) ZnuA, and an ABC transporter, which consists of ZnuB |
| GO:0046872 metal ion binding | IEA GO_REF:0000002 | TOO GENERAL | Summary: Metal ion binding from InterPro. Reason: Zinc ion binding (GO:0008270), accepted here, is_a metal ion binding. |
| GO:0071577 zinc ion transmembrane transport | IEA GO_REF:0000108 | ACCEPT | Summary: Zinc ion transmembrane transport, inferred from the transporter-activity row. Reason: ZnuABC moves zinc from the periplasm across the inner membrane; ZnuA is required for most cellular zinc accumulation. Supporting Evidence: PMID:26290475 Metal accumulation analyses revealed a significant 59.6% decrease in cellular Zn2+ due to loss of the SBP |
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Download this section (compressed HTML)Q: Which pathways supply the remaining ~40% of zinc in a znuA mutant, and do they share ZnuB/ZnuC?
Experiment: Measure 65Zn uptake kinetics in znuA, znuB, znuC and combined mutants of the zinc-limitation-induced import systems to partition uptake among them.
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