Structural bases of protein kinase CK2 inhibition

Protein kinase CK2 is involved in many fundamental aspects of normal cell life, but it is also able to establish favourable conditions for tumorigenesis. CK2 is elevated in various cancers, it is a potent suppressor of apoptosis, it strongly promotes cell survival, it strengthens the multi-drug resistant phenotype and can be considered a valuable drug target for cancer therapy. In this review, the structural bases of CK2 inhibition deduced from the analysis of crystal structures of CK2alpha-inhibitor complexes are presented and discussed. The best ATP-competitive inhibitors show an adequate hydrophobic character, an excellent shape complementarity with the unique active site of CK2, and the ability to establish polar interactions with both the hinge region and the positive electrostatic area near the conserved water W1 and the Lys68-Glu81 salt bridge. The state of the art of non-ATP-competitive inhibitors is also presented.