Casein kinase 2 (CK2) is a ubiquitous pleiotropic proliferation-associated serine/threonine protein kinase. Similar to protein kinase A, CK2 is a tetramer made up from two different subunits α2β2. The catalytic α-subunit corresponds to the C-subunit of PKA, the non-catalytic β-subunit is unique and differs from the R-subunit of PKA in all known features.The recombinant protein kinase CK2α from Zea mays was expressed in E.coli as a non fusion protein and purified by several chromatography steps (phosphocellulose, Superose 6, Resource Q). It is less prone to degradation than the human counterpart. The α-subunit is constitutively active and suitable for labeling casein kinase 2 αsubstrates. It is shown to be extremely salt sensitive, the highest activity is shown without salt.