Protein Kinase Casein Kinase 2 (PKCK2, also called CK2) is a ubiquitous Ser/Thr kinase expressed in all eukaryotes. PKCK2 is a tetramer composed of two catalytic kinase domains, alpha subunits, and two identical regulatory beta subunits. It has been implicated in cell cycle control , DNA repair, regulation of the circadian rhythm, and other cellular processes. Recombinant human PKCK2, fused to His tag at N-terminus, was expressed in E.coli and purified by using conventional chromatography techniques.