Interaction sites between catalytic and regulatory subunits in human protein kinase CK2 holoenzymes as indicated by chemical cross-linking and immunological investigations

The tetrameric structure of protein kinase CK2 is formed by cross-linkages between residues 55-70 on the beta subunit with either the residues 65-80 on the alpha subunit or residues 66-81 on the alpha prime subunit. The presence of these cross-linkages was detected by fusing CK2 with carbodiimide, subjecting them to proteolytic digestion and analyzing the digestion products. These contact sites between the beta and alpha subunits were found to be responsible for maintaining the activity and stability of the CK2 enzyme.