Physiological Role for Cation Channels in Bacteria

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SUMMARY Tetrameric cation channels are widely conserved among all species. While bacterial cation channels are often used in structural and biophysical assays as models for their eukaryotic homologs, little is known about their physiological role in bacteria. Escherichia coli (E. coli) possesses a single tetrameric K+ channel, kch, which bears high sequence homology to eukaryotic K+ channels. The generation of a viable ∆kch strain created as part of a large E. coli single-gene knockout collection led to kch being categorized as a non-essential protein, and the functional role of this putative K+ channel has remained unknown. Preliminary data demonstrates that Kch is actually an essential protein and that ∆kch strains acquire suppressor mutations in order to remain viable. These suppressor mutations provide important clues as to which metabolic processes utilize the channel and has revealed a potential physiological role for Kch. Based on these results, the following aims are proposed: (1) to characterize the functional properties of the kch K+ channel; (2) to determine how Kch function affects E. coli physiology; and (3) to expand these findings to other bacteria to elucidate the conserved functions of bacterial cation channels. The results of this work will expand knowledge on the role of cation channels in bacterial physiology. Given the prevalence of these channels in pathogenic bacteria, understanding how cation channels benefit them may reveal how these proteins could be exploited as novel drug targets.