Sturgill T W, Ray L B, Erikson E, Maller J L
Department of Internal Medicine, University of Virginia School of Medicine, Charlottesville 22903.
Nature. 1988 Aug 25;334(6184):715-8. doi: 10.1038/334715a0.
Ribosomal protein S6 is a component of the eukaryotic 40S ribosomal subunit that becomes phosphorylated on multiple serine residues in response to a variety of mitogens, including insulin, growth factors, and transforming proteins of many oncogenic viruses. Recently, an activated S6 kinase (S6 K II) has been purified to homogeneity from Xenopus eggs, and characterized immunologically and at the molecular level. Purified S6 K II can be deactivated in vitro by incubation with either protein phosphatase 1 or protein phosphatase 2A. Reactivation and phosphorylation of S6 K II occurs in vitro with an insulin-stimulated microtubule-associated protein-2 (MAP-2) protein kinase which is itself a phosphoprotein that can be deactivated by protein phosphatase 2A. These studies suggest that a step in insulin signalling involves sequential activation by phosphorylation of at least two serine/threonine protein kinases.
核糖体蛋白S6是真核生物40S核糖体亚基的一个组成部分，在受到多种促细胞分裂剂（包括胰岛素、生长因子以及许多致癌病毒的转化蛋白）刺激时，其多个丝氨酸残基会发生磷酸化。最近，一种活化的S6激酶（S6 K II）已从非洲爪蟾卵中纯化至同质，并在免疫学和分子水平上进行了表征。纯化后的S6 K II在体外与蛋白磷酸酶1或蛋白磷酸酶2A一起孵育时可被失活。S6 K II的再激活和磷酸化在体外由胰岛素刺激的微管相关蛋白2（MAP-2）蛋白激酶发生，该激酶本身是一种磷蛋白，可被蛋白磷酸酶2A失活。这些研究表明，胰岛素信号传导中的一个步骤涉及至少两种丝氨酸/苏氨酸蛋白激酶通过磷酸化进行的顺序激活。
