Zinc(II) tolerance in Escherichia coli K-12: evidence that the zntA gene (o732) encodes a cation transport ATPase

Mol Microbiol. 1997 Sep;25(5):883-91. doi: 10.1111/j.1365-2958.1997.mmi518.x.


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.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adenosine Triphosphatases / genetics
  • Adenosine Triphosphatases / physiology
  • Biological Transport / drug effects
  • Cadmium / metabolism
  • Cations
  • Chromosome Mapping
  • Cobalt / metabolism
  • DNA Transposable Elements / genetics
  • DNA Transposable Elements / physiology
  • DNA, Bacterial / analysis
  • DNA, Bacterial / genetics
  • Drug Tolerance / genetics
  • Escherichia coli / classification
  • Escherichia coli / genetics
  • Escherichia coli / physiology*
  • Genes, Bacterial / genetics*
  • Genetic Complementation Test
  • Metals / metabolism
  • Mutation / genetics
  • Mutation / physiology
  • Sequence Analysis, DNA
  • Zinc / physiology*


  • Cations
  • DNA Transposable Elements
  • DNA, Bacterial
  • Metals
  • Cadmium
  • Cobalt
  • Adenosine Triphosphatases
  • Zinc