Structural basis of cyclin-dependent kinase activation by phosphorylation

Area of Science:

• Structural biology
• Molecular biology
• Biochemistry

Background:

• Cyclin-dependent kinases (CDKs) are key regulators of the cell cycle.
• Full activation of CDK-cyclin complexes requires phosphorylation of the CDK subunit.
• The regulatory T-loop of CDKs plays a critical role in kinase activity.

Purpose of the Study:

• To determine the crystal structure of the phosphorylated CDK2-CyclinA-ATP gamma S complex.
• To elucidate the structural role of phosphorylation in CDK2 activation.
• To understand the interactions mediated by the phosphate group within the complex.

Main Methods:

• X-ray crystallography at 2.6 A resolution.
• Structural comparison of phosphorylated and unphosphorylated CDK2-CyclinA complexes.

Main Results:

• The crystal structure of the phosphorylated CDK2-CyclinA-ATP gamma S complex was determined.
• The activating phosphate group on the CDK2 T-loop is buried and its charge is neutralized by arginine residues.
• Significant conformational changes in the T-loop (up to 7 A) were observed upon phosphorylation, impacting the substrate binding site and complex stability.

Conclusions:

• The activating phosphate group acts as a major organizing center within the CDK2-CyclinA complex.
• Phosphorylation-induced structural rearrangements are critical for CDK2-CyclinA complex function.
• Understanding these structural dynamics provides insights into cell cycle regulation.