Characterization of Small Proteins that Regulate Two Component Systems in Escherichia coli

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ABSTRACT Bacteria are ubiquitous and need to survive in numerous environmental conditions. Two component systems (TCS), which are found in all domains of life and transduce a variety of external and internal signals into changes in gene expression, are critical to this survival. In the model Gram-negative organism, Escherichia coli, there are over 20 TCS that are able to respond to different stimuli. These systems are comprised of at least one sensor histidine kinase at the membrane and one response regulator, which is generally a transcription factor. These proteins work in coordination to activate a subset of genes to help ensure survival during specific stressful environments. Small proteins of around 50 amino acids or fewer generally have been overlooked in standard genetic and biochemical experiments. However, small proteins have been found to regulate a number of responses including virulence in Salmonella, sporulation in Bacillus subtilis, and the low magnesium induced PhoPQ TCS in E. coli. The MgrB small protein inhibits the PhoPQ TCS while another small protein, SafA, activates this TCS. We hypothesize that there are other small proteins in E. coli that also regulate the activities of TCS. This proposal will use targeted biochemical and global characterization of two candidate small proteins: YshB and ArcB-C to identify their mechanism of actions. Additionally, a screen will be created to identify small protein regulators of other TCS systems in E. coli and other bacteria. The results from this proposal will add to the growing knowledge about small proteins. More broadly, the information gained from this study could potentially be applied to eukaryotic kinases as they act similarly to bacterial kinases, which likely are also modulated by small proteins.