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Structural basis for methylesterase CheB regulation by a phosphorylation-activated domain
S Djordjevic1, P N Goudreau, Q Xu
1Howard Hughes Medical Institute, Center for Advanced Biotechnology and Medicine, and Department of Biochemistry, University of Medicine and Dentistry of New Jersey, 679 Hoes Lane, Piscataway, NJ 08854, USA.
Summary
The crystal structure of methylesterase CheB reveals how phosphorylation regulates bacterial chemotaxis. Unphosphorylated CheB inhibits its own activity, while phosphorylation activates it by altering domain interactions.
Area of Science:
- Biochemistry
- Structural Biology
- Microbiology
Background:
- Bacterial chemotaxis relies on receptor modification by CheB and CheR.
- Methylesterase CheB is a key enzyme in regulating chemotaxis signaling output.
- CheB's activity is controlled by phosphorylation, acting as a response regulator.
Purpose of the Study:
- To determine the X-ray crystal structure of methylesterase CheB.
- To elucidate the mechanism of CheB regulation by phosphorylation.
- To explore the structural relationship between CheB and CheR.
Main Methods:
- X-ray crystallography
- Molecular replacement using independent domain models
- Structural comparison with related proteins
Main Results:
- The structure of CheB reveals an N-terminal regulatory domain and a C-terminal catalytic domain.
- In unphosphorylated CheB, the N-terminal domain inhibits the catalytic domain's active site.
- Phosphorylation is proposed to induce a conformational change, releasing inhibition and activating the enzyme.
- Structural similarities between CheB and CheR suggest functional or evolutionary links.
Conclusions:
- CheB activity is regulated by a phosphorylation-induced conformational change that alters domain interactions.
- The structure provides insights into the mechanism of bacterial chemotaxis signal modulation.
- Comparative analysis highlights conserved and divergent protein-protein interaction surfaces within the response regulator family.