RIG: Structural Biology of the Soil Bacterium M. xanthus Development and Motility

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Intellectual merit. The soil bacterium Myxococcus xanthus is a model organism for studying prokaryotic chemosensory signal transduction. This bacterium contains eight chemosensory systems that regulate developmental gene expression, motility, and biofilm formation. The focus of this project is to elucidate the regulatory mechanisms of signal transduction in the Che3 and Frz chemosensory systems, which are critical for spore development and motility, respectively. The Che3 system regulates transcription of important developmental genes in response to outer membrane stress. This regulation is derived through the recently identified regulatory protein, CrdC (chemosensory regulator of development protein C). This investigator's preliminary findings indicate that CrdC modulates downstream signaling and sporulation by forming a regulatory complex with CheW3. Solution NMR methods will be used to determine the structures of CheW3 and CrdC and define the residues that mediate their interaction. These structures will provide the foundation for understanding the biochemical and structural features required for Che3 chemosensory regulation. The Frz chemosensory system and the protein MglA are critical regulators of motility. The Frz system is capable of activating MglA by an unknown mechanism. Activated MglA, in turn, is critical for regulating motility through the interaction with downstream effector proteins. The MglA protein has homology to eukaryotic GTPases, but its ability to bind and hydrolyze guanine nucleotides has not been determined. This study will use biochemical and biophysical approaches to define the nucleotide-binding properties of MglA and the requirements for interacting with downstream signaling effectors. The results from these fundamental studies will provide key structural and biophysical insights into the mechanism of Che3 and Frz chemosensory regulation and the framework for future research towards developing a comprehensive structural and mechanistic picture of chemosensory regulation in M. xanthus. Broader impacts. Exciting students about science and biochemical research is critical for fostering science-based careers. The principal investigator will engage students early in their undergraduate career in two ways. First, he will design and implement a new laboratory section for the existing experimental Biochemistry course that features biophysical experiments. This novel section will complement the existing didactic courses in biophysics and expose undergraduate students to quantitative methods and biophysical techniques. Second, he will initiate a new program to provide summer research opportunities to under-represented minority students. This program will be funded by the RIG grant and the Department of Biochemistry. Collectively, these strategies will help provide the necessary academic and research background necessary to attract and retain talented undergraduate students in the sciences.