Wong T W, Goldberg A R
J Biol Chem. 1984 Jul 10;259(13):8505-12.
The major species of tyrosine protein kinase of rat liver, has been purified to near homogeneity from liver cytosol. When the kinase was incubated with MnCl2 and [gamma-32P]ATP, two phosphoproteins with molecular masses of 72 and 75 kilodaltons were observed. The purified kinase, called p75 kinase, phosphorylates [Val5]angiotensin II, casein, vinculin, and a 34-kilodalton protein isolated from chicken embryo fibroblasts. However, it does not phosphorylate histones or IgG from Rous sarcoma virus tumor-bearing rabbits. The kinase does not contain any of the major antigenic determinants found in retroviral tyrosine protein kinases or in epidermal growth factor-receptor kinase. p75 kinase activity, as well as viral tyrosine protein kinase activity, is stimulated by heparin. Phosphorylation of angiotensin is also stimulated by high ionic strength. In contrast, casein phosphorylation by the kinase appeared to be inhibited by high salt. Kinetic properties of p75 kinase have been determined and have revealed some striking differences from those of most other tyrosine protein kinases. For instance, p75 kinase exhibits rather stringent dependence for its activity on ATP as phosphoryl donor and Mn2+ as divalent cation.
大鼠肝脏中的主要酪氨酸蛋白激酶已从肝细胞溶胶中纯化至近乎同质。当该激酶与氯化锰和[γ-32P]ATP一起孵育时，观察到两种分子量分别为72和75千道尔顿的磷蛋白。这种纯化的激酶，称为p75激酶，可磷酸化[缬氨酸5]血管紧张素II、酪蛋白、纽蛋白以及从鸡胚成纤维细胞中分离出的一种34千道尔顿的蛋白质。然而，它不会磷酸化来自携带劳斯肉瘤病毒肿瘤的兔子的组蛋白或IgG。该激酶不包含在逆转录病毒酪氨酸蛋白激酶或表皮生长因子受体激酶中发现的任何主要抗原决定簇。p75激酶活性以及病毒酪氨酸蛋白激酶活性都受到肝素的刺激。血管紧张素的磷酸化也受到高离子强度的刺激。相比之下，该激酶对酪蛋白的磷酸化似乎受到高盐的抑制。已确定了p75激酶的动力学特性，并揭示了其与大多数其他酪氨酸蛋白激酶的一些显著差异。例如，p75激酶的活性对作为磷酰供体的ATP和作为二价阳离子的Mn2+表现出相当严格的依赖性。
