Meggio F, Boldyreff B, Issinger O G, Pinna L A
Dipartimento di Chimica Biologica, Università di Padova, Italy.
Biochim Biophys Acta. 1993 Jul 10;1164(2):223-5. doi: 10.1016/0167-4838(93)90252-m.
Two mutants of human casein kinase-2 beta-subunit with short deletions at either their amino (delta 1-4) or carboxy (delta 209-215) terminal side have been created that have lost the capability to undergo autophosphorylation and p34cdc2 mediated phosphorylation, respectively. Both mutants give rise to reconstituted CK2 holoenzymes displaying basal catalytic activity, thermostability and responsiveness to polylysine, identical to those of wild-type holoenzyme, whose reconstitution, moreover, is not affected by previous phosphorylation of the beta-subunit at either its N-terminal or C-terminal sites. Unlike the wild-type beta and beta(delta 209-215), however, beta(delta 1-4) fails to confer to the reconstituted holoenzyme the typical responsiveness to NaCl stimulation. These results suggest that while neither the autophosphorylation nor the p34cdc2 phosphorylation sites are required for conferring a stable structure and full catalytic activity to CK2, the autophosphorylation site is implicated in the NaCl-dependent fine tuning of CK2 activity.
已构建出两个人类酪蛋白激酶2β亚基的突变体，它们分别在氨基端（δ1 - 4）或羧基端（δ209 - 215）有短片段缺失，并且分别丧失了进行自身磷酸化和p34cdc2介导的磷酸化的能力。这两个突变体均产生了重组的CK2全酶，其显示出与野生型全酶相同的基础催化活性、热稳定性和对聚赖氨酸的反应性，此外，β亚基在其N端或C端位点的先前磷酸化对其重组没有影响。然而，与野生型β和β（δ209 - 215）不同，β（δ1 - 4）不能赋予重组全酶对NaCl刺激的典型反应性。这些结果表明，虽然自身磷酸化位点和p34cdc2磷酸化位点对于赋予CK2稳定结构和完全催化活性都不是必需的，但自身磷酸化位点与CK2活性的NaCl依赖性微调有关。
