Biochemical evidence that the N-terminal segments of the alpha subunit andthe beta subunit play interchangeable roles in the activation of protein kinase CK2

The concept that the amino-terminal segment plays a role in conferring high basal activity to protein kinase CK2 alpha subunit has been validated by g enerating two mutants (Y26F and Delta 2-6) which are defective both in cata lytic activity and in thermal stability. The additional finding that the ac tivity of the two mutants is fully restored upon association with the regul atory beta subunit, in conjunction with the observation that synthetic pept ides reproducing the N-terminal segment (1-30) and the activation loop (175 -201) of CK2 alpha counteract the functional effects of the C-terminal doma in of the beta subunit, is consistent with a mechanism of activation of CK2 where the N-terminal domain of alpha and the C-terminal domain of beta pla y interchangeable roles. (C) 1998 Federation of European Biochemical Societ ies.