Overall structure of CK2α at 1.06 Å resolution. (a) A ribbon model. The five alternative conformations were observed in the interior of the molecule (black dashed box). (b) A solvent accessible surface. The N-terminal extension, N-lobe, hinge region, αD-helix and C-lobe are displayed by violet, blue, yellow, orange, light-blue ribbons, respectively. The nicotinic acid and ethylene glycol molecules are shown as ball and stick models. The alternative conformation loci are indicated by the red side chains.