Analysis of the kefA2 mutation suggests that KefA is a cation-specific channel involved in osmotic adaptation in Escherichia coli.
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.
McLaggan
Debra
D
Department of Molecular and Cell Biology, University of Aberdeen, Institute of Medical Sciences, Foresterhill, UK.
Jones
Michael A
MA
Gouesbet
Gwenola
G
Levina
Natasha
N
Lindey
Susanna
S
Epstein
Wolfgang
W
Booth
Ian R
IR
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*
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