The genome of the hypervirulent strain of Clostridioides difficile (Cd) R20291 encodes for 54 HKs and 57 RR proteins comprising two-component signal transduction pathways that allow the organism to sense and respond (adapt) to environmental changes. The West group embarked on the study of select TCS proteins that play essential roles in antibiotic resistance, spore formation, and virulence in the obligate anaerobe Cd, as part of a collaborative project funded by the Price Family Foundation. Our current projects involve in vivo knockout studies in Cd and in vitro characterization of recently identified TCS proteins implicated in sporulation in Cd. Spores are known to be the major cause of disease transmission to new hosts and are the main source of disease recurrence in patients with C. difficile infections (CDIs).
Ann H. West
Grayce B. Kerr Centennial Chair
Director, Oklahoma COBRE in Structural Biology
Associate Vice President for Research and Partnerships
Signal Transduction in Pathogenic Bacteria and Yeast
Signaling pathways are widely implicated in pathogenesis and virulence. Two-component systems (TCS) are highly conserved signal transduction pathways found commonly in bacteria, yeast and plants. They contain a sensor histidine kinase (HK) and a response regulator (RR) protein. Upon sensing an environmental signal, the HK activates the RR protein through transfer of a phosphoryl group. This activation causes a conformational change in the RR protein which modulates its function and stimulates a change (adaptation) in the cell. These pathways present excellent targets for new antimicrobial therapeutics because they are unique to lower eukaryotes and plants. The West group’s long-term goal is to determine global signal-to-response regulatory circuitry in various pathogenic bacteria from sensory histidine kinase function to response regulator-specific gene regulons.
TCS in Clostridioides difficile
Phosphorelay signaling pathway in Saccharomyces cerevisiae
Branched multi-step His-Asp phosphorelay signaling pathways are central to the ability of fungal cells to respond to environmental stress. In the yeast S. cerevisiae, the histidine-containing phosphotransfer (HPt) protein Ypd1 is required for phosphoryl group transfer from Sln1, a membrane-bound sensor hybrid histidine kinase (HHK) to two response regulator (RR) proteins (Ssk1 in the cytoplasm and Skn7 in the nucleus), which mediate osmotic and cell wall stress responses. The West group studies the role of phosphorylation and dephosphorylation in regulating protein function within the yeast His-Asp phosphorelay signaling pathway. Our recent X-ray crystallographic studies of the Ypd1 HPt protein in complex with its upstream and downstream receiver domain, provides an excellent foundation for elucidating the molecular interactions within this phosphorelay signaling system.