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. |
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| 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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Main Points of the Paper
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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 |
|
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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Notes
References
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