Crystallization and preliminary X-ray diffraction analysis of the regulatory subunit of human protein kinase CK2

Protein kinase CK2 is a tetramer composed of two α catalytic subunits and two β regulatory subunits. A C-terminal truncated form of the β subunit has been overproduced in Escherichia coli and purified to homogeneity. Two crystal forms of the truncated protein which diffract to at least 2 Å resolution have been obtained. Form I belongs to the monoclinic space group P2₁, with unit-cell parameters a = 49.9, b = 92.9, c = 53.7 Å, β = 96.3°, and yields plate-like crystals. Form II belongs to the tetragonal space group P4₂2₁2, with unit-cell parameters a = 132.19, b = 132.19, c = 63.79 Å, and produces rod-shaped crystals. Both crystal forms have a functional dimer in the crystal asymmetric unit.