Crystal structures of catalytic and regulatory subunits of rat protein kinase CK2

Protein kinase CK2 consists of two catalytic subunits (CK2 alpha) and two regulatory subunits (CK2 beta). Here, we report the crystal structures of rat CK2 alpha mutant (rCK2 alpha-Delta C, 1-335) and CK2 beta (rCK2 beta). The overall topology of rCK2 alpha-Delta C and rCK2 beta are very similar to the human enzyme, although large structural differences could be observed in the N-terminal domain of rCK2 alpha-Delta C. Our reported structure of rCK2 alpha-Delta C is in the close conformation state while the counterpart hCK2 alpha is in the open conformation state, indicating the conformation of CK2 alpha molecule has high plasticity. The structure of rCK2 beta represents the conformation of free CK2 beta. Upon CK2 alpha binding, the C-terminal region undergoes a drastic conformational change. The major region of interaction within the interface of CK2 alpha/CK2 beta may serve as a bridge to transmit the conformational change and thus regulate the activity of CK2 alpha.