Ramamoorthy S, Balasubramanian A S
Department of Neurological Sciences, Christian Medical College Hospital, Vellore, India.
Arch Biochem Biophys. 1989 Feb 15;269(1):148-55. doi: 10.1016/0003-9861(89)90095-7.
Tyrosine phosphorylation of a 55- and 60-kDa protein was observed when EDTA-treated P2 membrane fraction from monkey basal ganglia was incubated with [gamma-32P]-ATP in the presence of Zn2+. Other metal ions were less effective in this phosphorylation. The effect of Zn2+ did not appear to be due to its inhibition of a tyrosine phosphatase. In the presence of Mg2+/Triton X-100 instead of Zn2+, phosphorylation on tyrosine residues of a 17-kDa protein and the external substrate poly(Glu, Tyr) 4:1 copolymer was observed. Both Mg2+ and Triton X-100 were essential for this and Zn2+ inhibited both of these phosphorylations. Convincing evidence for the existence of Zn2+-dependent and Mg2+/Triton X-100-dependent tyrosine protein kinases was obtained when the two kinases could be separated by extraction of the membranes by Triton X-100. The Zn2+-dependent phosphorylation was present exclusively in the Triton-solubilized supernatant whereas the Mg2+/Triton X-100-dependent phosphorylation was found associated with the Triton-insoluble membrane fractions. Externally added histone could also be phosphorylated on tyrosine residues in a Zn2+- or Mg2+/Triton X-100-dependent manner by the supernatant or membrane fraction, respectively.
当来自猴基底神经节的经乙二胺四乙酸（EDTA）处理的P2膜组分在锌离子（Zn2+）存在的情况下与[γ-32P] -ATP一起孵育时，观察到一种55 kDa和60 kDa蛋白质的酪氨酸磷酸化。其他金属离子在这种磷酸化反应中的效果较差。Zn2+的作用似乎并非由于其对酪氨酸磷酸酶的抑制。在存在镁离子（Mg2+）/聚乙二醇辛基苯基醚（Triton X-100）而非Zn2+的情况下，观察到一种17 kDa蛋白质和外部底物聚（谷氨酸，酪氨酸）4:1共聚物的酪氨酸残基发生磷酸化。Mg2+和Triton X-100对此都是必需的，并且Zn2+会抑制这两种磷酸化反应。当通过用Triton X-100提取膜来分离这两种激酶时，获得了存在依赖于Zn2+和依赖于Mg2+/Triton X-100的酪氨酸蛋白激酶的确凿证据。依赖于Zn2+的磷酸化仅存在于经Triton溶解的上清液中，而依赖于Mg2+/Triton X-100的磷酸化则与不溶于Triton的膜组分相关。外部添加的组蛋白也可以分别通过上清液或膜组分以依赖于Zn2+或依赖于Mg2+/Triton X-100的方式在酪氨酸残基上发生磷酸化。
