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Mutational analysis supports a structural model for the cell cycle protein kinase p34
J A Endicott1, P Nurse, L N Johnson
1Laboratory of Molecular Biophysics, Oxford University, UK.
Protein Engineering
|February 1, 1994
Summary
Structural models of the eukaryotic cell cycle protein p34 reveal key differences from cAPK, explaining substrate specificity. Phosphorylation sites near the active site likely inhibit p34 kinase activity.
Area of Science:
- Biochemistry
- Structural Biology
- Molecular Biology
Background:
- The eukaryotic cell cycle is regulated by proteins like p34, crucial for cell division.
- Understanding the structure of p34 is essential for elucidating its regulatory mechanisms and interactions.
Purpose of the Study:
- To derive structural models of the cell cycle control protein p34 from human, S. pombe, and S. cerevisiae.
- To compare these models with known kinase structures to understand substrate specificity and regulatory mechanisms.
Main Methods:
- Comparative structural modeling using crystallographic coordinates of cAMP-dependent protein kinase (cAPK) and inactive CDK2 apoenzyme.
- Analysis of conserved sequences and predicted active-site cleft composition.
Main Results:
- Structural models of p34 were generated, highlighting differences in catalytic sites compared to cAPK, suggesting varied substrate specificities.
- Key phosphorylation sites (Tyr15, Thr14) were localized near the active site, potentially inhibiting kinase activity.
- Conserved functional sequences (PSTAIRE, LYLIFEFL) and surface-exposed regions involved in protein interactions were identified.
Conclusions:
- The structural models provide insights into p34 function, substrate specificity, and regulation by phosphorylation.
- Identified surface regions and residues are predicted to mediate interactions with regulatory proteins like cyclin, p107wee1, and p80cdc25.