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Updated: Jul 30, 2026
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Unraveling Entropic Rate Acceleration Induced by Solvent Dynamics in Membrane Enzymes
Published on: January 16, 2016
Phosphorylation causes subtle changes in solvent accessibility at the interdomain interface of methylesterase CheB
C A Hughes1, J G Mandell, G S Anand
1Department of Chemistry and Biochemistry, University of California, San Diego, 9500 Gilman Dr, La Jolla, CA, 92093-0359, USA
Journal of Molecular Biology
|April 5, 2001
Summary
Phosphorylation of methylesterase CheB (CheB) subtly alters enzyme structure. This structural change, observed via hydrogen/deuterium exchange, enhances substrate access to the active site, enabling transient catalytic activity.
Area of Science:
- Biochemistry
- Structural Biology
- Enzymology
Background:
- Methylesterase CheB (CheB) regulates chemotaxis in bacteria.
- The unphosphorylated state of CheB features a regulatory domain inhibiting substrate access to the catalytic domain's active site.
- Phosphorylation at Asp56 activates CheB, but this active state is transient.
Purpose of the Study:
- To investigate the structural changes in CheB upon phosphorylation at Asp56.
- To determine how phosphorylation affects the solvent accessibility of different CheB domains.
- To understand the mechanism of CheB activation at a molecular level.
Main Methods:
- Determining the crystal structure of unphosphorylated CheB.
- Inducing transient phosphorylation of CheB at Asp56.
- Utilizing MALDI-TOF-detected amide hydrogen/deuterium exchange to probe solvent accessibility.
- Comparing solvent accessibility changes with an isolated catalytic domain fragment.
Main Results:
- Phosphorylation of Asp56 in CheB leads to a transiently active enzyme.
- No significant solvent accessibility changes were observed in the regulatory domain.
- Two specific regions within the catalytic domain (residues 199-203 and 310-317) showed increased solvent accessibility.
- The observed increase in accessibility was less than that seen upon complete regulatory domain detachment.
Conclusions:
- Phosphorylation of CheB induces subtle structural rearrangements at the interdomain interface.
- These subtle changes enhance substrate access to the active site, facilitating transient catalysis.
- The findings provide insights into the dynamic regulation of CheB activity.
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