Crystallization of a complex between human CDK6 and a virus-encoded cyclin is critically dependent on the addition of small charged organic molecules.

Abstract

Human CDK6 plays an important role in controlling entry into the eukaryotic cell cycle. An activated complex of human CDK6 with a viral cyclin from herpesvirus saimiri was purified to homogeneity and crystallized using polyethylene glycol 3350 as precipitant. Crystallization was critically dependent on a narrow range of calcium acetate concentration and the presence of sulfo-betaine 201 as additive. Crystals belong to the hexagonal space group P6(1)22 or P6(5)22, with unit-cell parameters a = b = 70.14, c = 448.77 A, gamma = 120 degrees, and diffract X-rays to at least 3.1 A resolution.