The CheC phosphatase regulates chemotactic adaptation through CheD.

Area of Science:

• Bacterial signaling pathways
• Molecular mechanisms of chemotaxis
• Protein-protein interactions in signal transduction

Background:

• The bacterial chemotaxis system regulates cell movement in response to chemical stimuli.
• CheY-phosphate (CheY-P) is a key response regulator, and CheA is its activating histidine kinase.
• CheC acts as a CheY-P phosphatase, with its activity enhanced by CheD, and is vital for chemotactic adaptation.

Purpose of the Study:

• To investigate the specific roles of CheC's functions in Bacillus subtilis chemotaxis.
• To dissect the contributions of CheD binding, CheY-P binding, and phosphatase activity to CheC's in vivo function.
• To elucidate the regulatory mechanism of CheC in the chemotaxis signal transduction pathway.

Main Methods:

• Generation and analysis of CheC point mutants in Bacillus subtilis.
• In vivo complementation assays to assess protein function.
• In vitro biochemical assays to determine binding affinities and enzymatic activity.
• Characterization of CheC-CheD and CheC-CheY-P interactions.

Main Results:

• Mutants were created to separate CheC's CheD binding, CheY-P binding, and phosphatase activities.
• CheC's ability to bind both CheY-P and CheD was found to be more critical for in vivo function than its phosphatase activity.
• CheY-P binding enhances CheC's affinity for CheD, which is essential for CheA activation by receptors.

Conclusions:

• CheC acts as a CheY-P-induced regulator of CheD.
• CheY-P binding to CheC sequesters CheD from chemoreceptors, facilitating chemotactic adaptation.
• This provides a feedback mechanism from the system's output (CheY-P) to the receptors, regulating chemotaxis.