Analysis of the kefA2 mutation suggests that KefA is a cation-specific channel involved in osmotic adaptation in Escherichia coli

Debbie McLaggan, M. A. Jones, N. Levina, Ian Rylance Booth, G. Gouesbet, S. Lindey, W. Epstein

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Abstract

Mechanosensitive channels play an essential role in the regulation of turgor pressure in bacteria. In Escherichia coli, there are multiple mechanosensitive channels that have been characterized genetically: MscL, YggB and KefA. In this report, we describe the cloning of the kefA gene, the organization of the KefA protein and the phenotype of a missense mutation, kefA, which affects the KefA mechanosensitive channel. The altered function of the channel is manifest through increased sensitivity to K+ during growth at low osmolarity and complete inhibition of growth in media containing high K+ concentrations (0.6 M) in the presence of betaine or proline. Growth in high Na+ medium (0.6 M NaCl plus 20 mM K+) is normal. Analysis of the cytoplasmic pools shows that the mutant cannot regulate the K+ content of the cytoplasm when grown in high K+ medium. However, regulation of pools of amino acids is essentially normal and the mutant can accumulate high pools of proline during growth inhibition. The mutant shows increased sensitivity to acid hypo-osmotic shock (transition from neutral to acid pH combined with a reduction in osmolarity). The data are consistent with abnormal regulation of KefA in the presence of high K+ concentrations and either betaine or proline.

Original languageEnglish
Pages (from-to)521-536
Number of pages15
JournalMolecular Microbiology
Volume43
Issue number2
DOIs
Publication statusPublished - 2002

Keywords

  • COMPATIBLE SOLUTE ACCUMULATION
  • POTASSIUM-TRANSPORT LOCI
  • MECHANOSENSITIVE CHANNEL
  • SALMONELLA-TYPHIMURIUM
  • ALKALINE-PHOSPHATASE
  • CYTOPLASMIC MEMBRANE
  • MULTIDRUG EFFLUX
  • ION CHANNELS
  • PROTEIN
  • MSCL

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