Allende C C, Allende J E
Programa de Biología Celular y Molecular, Instituto de Ciencias Biomédicas, Facultad de Medicina, Universidad de Chile, Santiago, Chile.
J Cell Biochem Suppl. 1998;30-31:129-36.
Protein kinase CK2 is a ubiquitous eukaryotic ser/thr protein kinase. The active holoenzyme is a heterotetrameric protein composed of catalytic (alpha and alpha') and regulatory (beta) subunits that phosphorylates many different protein substrates and appears to be involved in the regulation of cell division. Despite important structural studies, the intimate details of the interactions of the alpha catalytic subunits with the beta regulatory subunits are unknown. Recent evidence that indicates that both CK2 subunits can interact promiscuously with other proteins in a manner that excludes the binding of their complementary CK2 partners has opened the possibility that the phosphorylating activity of this enzyme may be regulated in a novel way. These alternative interactions could limit the in vivo availability of CK2 subunits to generate fully active holoenzyme CK2 tetramers. Likewise, variations in the ratio of alpha- and beta-subunits could determine the activity of several phosphorylating and dephosphorylating activities. The promiscuity of the CK2 subunits can be extrapolated to a more widespread phenomenon in which "wild-card" proteins could act as general switches by interacting and regulating several catalytic activities.
蛋白激酶CK2是一种普遍存在的真核丝氨酸/苏氨酸蛋白激酶。活性全酶是一种由催化亚基（α和α'）和调节亚基（β）组成的异源四聚体蛋白，它能磷酸化许多不同的蛋白质底物，似乎参与细胞分裂的调节。尽管有重要的结构研究，但α催化亚基与β调节亚基相互作用的具体细节仍不清楚。最近有证据表明，CK2的两个亚基都可以与其他蛋白质随意相互作用，这种方式排除了它们互补的CK2伙伴的结合，这就开启了这种酶的磷酸化活性可能以一种新方式被调节的可能性。这些替代性相互作用可能会限制CK2亚基在体内生成完全活性的全酶CK2四聚体的可用性。同样，α亚基和β亚基比例的变化可能决定几种磷酸化和去磷酸化活性的活性。CK2亚基的随意性可以外推到一种更广泛的现象，即“百搭”蛋白可以通过相互作用和调节几种催化活性来充当通用开关。
