A Molecular Dynamics Study of the Cyclin-Dependent Kinase-2 (CDK2) with Substrate Peptide (HHASPRK), Inhibition of CDK2 by Phosphorylation

I. Bártová¹, M. Otyepka², Z. Kříž¹, and J. Koča¹

¹National Centre for Biomolecular Research, Faculty of Science, Masaryk University, Kotlářská 2, 611 37 Brno, Czech Republic.

²Department of Physical Chemistry, Faculty of Science, Palacký University Olomouc, tř. Svobody 26, 771 46 Olomouc, Czech Republic.

The cyclin-dependent kinase, CDK2, regulates the eukaryotic cell cycle at the G1 – S boundary. CDKs activity is regulated by complex mechanism including binding to positive regulatory subunit and phosphorylation at positive and/or negative regulatory sites [1]. For activation CDK2 requires binding to Cyclin A or Cyclin E. The CDK2 obtains full activity after phosphorylation of the threonine residue (T160) in the activation segment (T-loop) [2]. CDK2 catalyzes the phosphoryl transfer of the adenosine-5´-triphosphate (ATP) g-phosphate to serine or threonine hydroxyl in the protein substrate. The CDKs activity is inhibited in several ways, for example, by (de)phosphorylation, interaction with various natural protein inhibitors [3,4], etc. The CDK2 can be negatively regulated by phosphorylation at Y15 and, to a lesser extent, at T14 in the glycine-rich loop (G-loop) [5].

This work describes behavior of the fully active CDK2 (pT160-CDK2/Cyclin A/ATP complex) with substrate peptide (HHASPRK) and CDK2 inhibited by phosphorylation at T14, Y15, and T14/Y15 residues altogether in the G-loop using molecular dynamics simulations with the Cornell et al. force field as implemented in the AMBER software package [6]. Inhibited complexes of CDK2 were prepared from pT160-CDK2/Cyclin A/HHASPRK/ATP (1QMZ PDB ID code) by phosphorylation of the T14 and/or Y15 residues. Enzyme dynamics was studied during 8 ns long trajectory. Differences in conformational behavior of key residues for substrate binding and phosphoryl transfer of fully active vs. inhibited CDK2 will be presented.

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