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Open Access Thesis
Molecular & Cellular Biology
Master of Science (M.S.)
Year Degree Awarded
Month Degree Awarded
In Caulobacter crescentus, progression through the cell cycle is regulated by the AAA+ protease ClpXP, and there are several classes of cell-cycle substrates that require adaptors in order to be degraded. CpdR, a single domain-response regulator, binds the N-terminal domain of ClpXP and primes the protease for degradation of downstream factors (Lau et al., 2015). The ability of CpdR to bind ClpX is regulated by its phosphorylation state. In the unphosphorylated state, CpdR binds ClpXP and guides its localization to the cell pole during the swarmer to stalked transition, where CpdR is mediates degradation of substrates such as PdeA. Phosphorylation of response regulator receiver domains requires magnesium as a cofactor to stabilize the phosphorylated aspartate and reciprocally, phosphorylated receiver domains bind magnesium more effectively. While it is understood that CpdR primers ClpX for substrate degradation, the mechanism by which it does so has remained unclear. Using CollabFold, we identified putative residues involved in CpdR-ClpX binding and validated them using a BACTH screening. In vitro, we characterized the role that magnesium plays in regulating CpdR binding to ClpX. In this work, we directly test the role of magnesium in CpdR priming of ClpXP to show that magnesium may play a regulatory role in CpdR-mediated degradation, and thus binding to ClpX. We identify residues in ClpX that seem to be important for CpdR binding, which prior to this work was not clear.
Barker, Kimberly E., "Elucidating the Priming Mechanism of ClpXP Protease by Single-Domain Response Regulator CpdR in Caulobacter crescentus" (2023). Masters Theses. 1359.