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Activity of the MAP kinase ERK2 is controlled by a flexible surface loop
1Department of Biochemistry, University of Texas Southwestern Medical Center at Dallas 75235, USA.
Structure (London, England : 1993)
|March 15, 1995
Summary
Mutation of Y185 in ERK2 significantly destabilizes the enzyme's low-activity conformation, revealing its critical role in regulating kinase activity. T183 is less crucial for this inactive state.
Area of Science:
- Biochemistry
- Molecular Biology
- Enzymology
Background:
- Mitogen-activated protein (MAP) kinase, ERK2, is a key enzyme in the Ras-activated protein kinase cascade.
- ERK2 activation depends on phosphorylation at Y185 and T183, located in the phosphorylation lip near the catalytic site.
Purpose of the Study:
- To investigate the role of Y185 and T183 residues in maintaining the low-activity conformation of ERK2.
- To understand how these residues influence enzyme regulation and activation.
Main Methods:
- Crystallographic analysis of four ERK2 mutants: T183E, Y185E, Y185F, and T183E/Y185E.
- Assays of phosphorylation-site mutants to evaluate conformational changes and enzyme activity.
Main Results:
- Mutation of Y185 (Y185E) caused significant disorder in the phosphorylation lip and adjacent regions.
- Conservative substitution Y185F also induced substantial conformational changes.
- Mutation T183E resulted in minimal conformational changes.
- A potential phosphotyrosine binding site in the active enzyme was identified.
Conclusions:
- The phosphorylation lip's stability is low and highly dependent on Y185, not T183.
- Modest binding energy is sufficient to dislodge the lip for phosphorylation.
- Y185 and T183 are crucial for conformational changes during kinase/phosphatase binding and activation, contributing to ERK2's tight control.