title: Analysis of the kefA2 mutation suggests that KefA is a cation-specific channel involved in osmotic adaptation in Escherichia coli.
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.
authors: Department of Molecular and Cell Biology, University of Aberdeen, Institute of Medical Sciences, Foresterhill, UK.
authors: Debra
authors: D
authors: McLaggan
authors: Michael A
authors: MA
authors: Jones
authors: Gwenola
authors: G
authors: Gouesbet
authors: Natasha
authors: N
authors: Levina
authors: Susanna
authors: S
authors: Lindey
authors: Wolfgang
authors: W
authors: Epstein
authors: Ian R
authors: IR
authors: Booth
mesh_terms: D000143:Acids; D000222:Adaptation, Physiological; D001426:Bacterial Proteins / Q000235:genetics / Q000502:physiology*; D002412:Cations; D004926:Escherichia coli / Q000235:genetics / Q000502:physiology*; D029968:Escherichia coli Proteins / Q000502:physiology*; D005798:Genes, Bacterial; D018698:Glutamic Acid / Q000378:metabolism; D016296:Mutagenesis; D009994:Osmolar Concentration; D009995:Osmosis; D011188:Potassium / Q000378:metabolism; D015221:Potassium Channels / Q000235:genetics / Q000502:physiology*; D011392:Proline; D014199:Trehalose / Q000096:biosynthesis; D014882:Water-Electrolyte Balance / Q000502:physiology*
chemical_list: D000143:Acids; D001426:Bacterial Proteins; D002412:Cations; D029968:Escherichia coli Proteins; D015221:Potassium Channels; C461459:kefA2 protein, E coli; D018698:Glutamic Acid; D011392:Proline; D014199:Trehalose; D011188:Potassium