title: Zinc(II) tolerance in Escherichia coli K-12: evidence that the zntA gene (o732) encodes a cation transport ATPase.
abstract: A transposon (Tn 10dCam) insertion mutant of Escherichia coli K-12 was isolated that exhibited hypersensitivity to zinc(II) and cadmium(II) and, to a lesser extent, cobalt(II) and nickel (II). The mutated gene, located between 75.5 and 76.2 min on the chromosome, is named zntA (for Zn(II) transport or tolerance). The metal-sensitive phenotype was complemented by a genomic DNA clone mapping at 3677.90-3684.60 kb on the physical map. Insertion of a kanamycin resistance (KnR) cassette at a SalI site in a subcloned fragment generated a plasmid that partially complemented the zinc(II)-sensitive phenotype. DNA sequence analysis revealed that the KnR cassette was located within the putative promoter region of an ORF (o732 or yhhO) predicted to encode a protein of 732 amino acids, similar to cation transport P-type ATPases in the Cpx-type family. Inverse PCR and sequence analysis revealed that the Tn 10dCam element was located within o732 in the genome of the zinc(II)-sensitive mutant. The zntA mutant had elevated amounts of intracellular and cell surface-bound Zn(II), consistent with the view that zntA+ encodes a zinc(II) efflux protein. Exposure of the zntA mutant to cobalt(II) and cadmium(II) also resulted in elevated levels of intracellular and cell surface-bound metal ions.
authors.affiliation: Division of Life Sciences, King's College London, UK.
authors.forename: S J
authors.initials: SJ
authors.lastname: Beard
authors.forename: R
authors.initials: R
authors.lastname: Hashim
authors.forename: J
authors.initials: J
authors.lastname: Membrillo-Hernández
authors.forename: M N
authors.initials: MN
authors.lastname: Hughes
authors.forename: R K
authors.initials: RK
authors.lastname: Poole
mesh_terms: D000251:Adenosine Triphosphatases / Q000235:genetics / Q000502:physiology; D001692:Biological Transport / Q000187:drug effects; D002104:Cadmium / Q000378:metabolism; D002412:Cations; D002874:Chromosome Mapping; D003035:Cobalt / Q000378:metabolism; D004251:DNA Transposable Elements / Q000235:genetics / Q000502:physiology; D004269:DNA, Bacterial / Q000032:analysis / Q000235:genetics; D004361:Drug Tolerance / Q000235:genetics; D004926:Escherichia coli / Q000145:classification / Q000235:genetics / Q000502:physiology*; D005798:Genes, Bacterial / Q000235:genetics*; D005816:Genetic Complementation Test; D008670:Metals / Q000378:metabolism; D009154:Mutation / Q000235:genetics / Q000502:physiology; D017422:Sequence Analysis, DNA; D015032:Zinc / Q000502:physiology*
chemical_list: D002412:Cations; D004251:DNA Transposable Elements; D004269:DNA, Bacterial; D008670:Metals; D002104:Cadmium; D003035:Cobalt; D000251:Adenosine Triphosphatases; D015032:Zinc