Activation of CDK2 by cyclin-A, mol. model

CDK2 is a cyclin-dependent kinase involved in regulation of the cell cycle. CDKs remain inactive until they associate with a regulatory subunit, a cyclin, and are subsequently phosphorylated on their "activation" segment. p53 indirectly inhibits the action of the cyclin/CDK2 complex, preventing the cell from proliferating. When p53 is absent of damaged, the cyclin/CDK2 complex becomes active and the cell can proliferate leading to cancer. This figure shows how X-ray crystallography has allowed us to understand atomic nature of activation of CDKL2 by cyclin-A. CDKs undergoes major structural changes involving the activation segment (cyan) and C-helix (gold).