PMID:11985727

Citation	McLaggan, D, Jones, MA, Gouesbet, G, Levina, N, Lindey, S, Epstein, W and Booth, IR (2002) Analysis of the kefA2 mutation suggests that KefA is a cation-specific channel involved in osmotic adaptation in Escherichia coli.Mol. Microbiol. 43:521-36
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.
Links	PubMed
Keywords	Acids; Adaptation, Physiological; Bacterial Proteins; Cations; Escherichia coli; Escherichia coli Proteins; Genes, Bacterial; Glutamic Acid; Mutagenesis; Osmolar Concentration; Osmosis; Potassium; Potassium Channels; Proline; Trehalose; Water-Electrolyte Balance
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Materials and Methods Used

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Phenotype Annotations

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Species	Taxon ID	Strain	Gene (if known)	OMP	Phenotype	Details	Evidence	Notes
Escherichia coli		RQ2	kefA2	no growth	Growth	in medium containing high levels of K+ in the presence of betaine	Growth Curve	gain-of-function mutation
Escherichia coli		RQ2	kefA2	no growth	Growth	in medium containing high levels of K+ in the presence of proline	Growth Curve	Figure 5A
Escherichia coli		RQ2	kefA2	no growth	Growth	in medium containing high levels of K+ in the presence of hydroxyectoine	Growth Curve	similar to Figure 5C, hydroxyectoine results not shown
Escherichia coli		RQ2	kefA2	partial growth inhibition	Growth	in medium containing high levels of K+ in the presence of ectoine	Growth Curve	data not shown
Escherichia coli		MJF502	kefA2 otsA::Tn10	reduced growth rate increased transitional lag upon K+ addition osmolarity-dependent	Growth	reduced growth rate after shifting from K20 to K20 + 0.3M KCl, but growth rate returned after 4 hours	Growth Curve
Escherichia coli		RQ2	kefA2	absent biphasic pattern of proline accumulation	Other	in the presence of 0.6M KCl, RQ2 failed to exhibit of second phase of proline accumulation	Biochemical Assay	Figure 7B
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