Significance of water molecules in the inhibition of cylin-dependent kinase 2 and 5 complexes.

Interest in CDK2 and CDK5 has stemmed mainly from their association with cancer and neuronal migration or differentiation related diseases and the need to design selective inhibitors for these kinases. In the present paper, eight Molecular Dynamics (MD) simulations are carried out to examine the importance of structure and dynamics of water in the active site of both CDK2 and CDK5 complexes with roscovitine and indirubin analogues. Together with previous results, the current work shows a highly conserved water-involved hydrogen bonding (HB) network in both CDK2- and CDK5-indirubin combinations to complete information from the X-ray crystallography. The simulations suggest the importance of such a network for combining the inhibitor to the host protein as well as the significance of using an activated CDK as a template when designing new inhibitors. Different binding patterns of roscovitine in CDK2 and CDK5 are detected during the simulations because of the different binding conformations of the group on the C2 side chain, which might offer a clue toward finding highly selective inhibitors with regards to CDK2 and CDK5.