Directed evolution reveals the mechanism of HitRS signaling transduction in Bacillus anthracis |
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| Authors: | Hualiang Pi Michelle L Chu Samuel J Ivan Casey J Latario Allen M Toth Sophia M Carlin Gideon H Hillebrand Hannah K Lin Jared D Reppart Devin L Stauff Eric P Skaar |
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| Institution: | 1. Department of Pathology, Microbiology, & Immunology, Vanderbilt University Medical Center, Nashville, Tennessee, United States of America;2. Vanderbilt Institute for Infection, Immunology, & Inflammation, Vanderbilt University Medical Center, Nashville, Tennessee, United States of America;3. Department of Biology, Grove City College, Grove City, Pennsylvania, United States of America;University of Texas Medical School at Houston, UNITED STATES |
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| Abstract: | Two component systems (TCSs) are a primary mechanism of signal sensing and response in bacteria. Systematic characterization of an entire TCS could provide a mechanistic understanding of these important signal transduction systems. Here, genetic selections were employed to dissect the molecular basis of signal transduction by the HitRS system that detects cell envelope stress in the pathogen Bacillus anthracis. Numerous point mutations were isolated within HitRS, 17 of which were in a 50-residue HAMP domain. Mutational analysis revealed the importance of hydrophobic interactions within the HAMP domain and highlighted its essentiality in TCS signaling. In addition, these data defined residues critical for activities intrinsic to HitRS, uncovered specific interactions among individual domains and between the two signaling proteins, and revealed that phosphotransfer is the rate-limiting step for signal transduction. Furthermore, this study establishes the use of unbiased genetic selections to study TCS signaling and provides a comprehensive mechanistic understanding of an entire TCS. |
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