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https://hdl.handle.net/2142/84843
Description
Title
The Chemotaxis Phosphatases cheC and cheX
Author(s)
Muff, Travis John
Issue Date
2007
Doctoral Committee Chair(s)
Ordal, George W.
Department of Study
Biochemistry
Discipline
Biochemistry
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Biology, Microbiology
Language
eng
Abstract
The CheY-P phosphatase CheC is important for chemotactic adaptation. The phosphatase ability of CheC is enhanced nearly five fold upon association with CheD. In this study, CheC mutants were generated in putative active site residues and the CheD binding helix. The mutants were examined for in vivo complementation, CheY binding, and phosphatase ability. Based on the active site mutants, a structural model for the association between CheC and CheY-P is proposed. Further, mutants were identified separating the three known abilities of CheC: CheD binding, CheY binding, and CheY-P phosphatase. Surprisingly, though the CheD and CheY binding mutants were non-functional in vivo, the phosphatase mutant showed partial CheC function. Therefore, the phosphatase ability is not as critical to in vivo CheC function as the ability to bind both CheY-P and CheD. Additionally, it was confirmed that CheY-P causes CheC to become a better binding site for CheD. Based on these results, a model is presented of CheC as a CheY-P induced regulator of CheD. By this model, CheA activation raises levels of CheY-P. The CheC then binds CheY-P and becomes a better binding site for CheD. This sequesters CheD from the chemoreceptors, thus de-exciting them and inducing adaptation of the chemotaxis system.
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