Golden A, Nemeth S P, Brugge J S
Proc Natl Acad Sci U S A. 1986 Feb;83(4):852-6. doi: 10.1073/pnas.83.4.852.
We have examined human and rabbit blood platelets for expression of pp60c-src, the normal cellular homolog of the transforming protein of Rous sarcoma virus. pp60c-src kinase activity was determined by an immune-complex kinase assay that uses enolase as the substrate, and pp60c-src protein levels were determined by an immunoblot assay. Lysates from platelets expressed high levels of pp60c-src-specific kinase activity and pp60c-src protein compared to the levels found in other tissues. pp60c-src was also found to be one of the major proteins phosphorylated in vitro in membranes isolated from platelets. Multiple protein species other than pp60c-src were also phosphorylated on tyrosine in the membrane phosphorylation reactions, and phosphotyrosine represented approximately equal to 80% of the total phosphoamino acid residues phosphorylated in the membranes. These results indicate that tyrosine kinases represent the major protein phosphorylating enzymes detected in isolated platelet membranes. Although the association of tyrosine kinase activity with many viral oncogene products and cellular growth hormone receptors has suggested a role for these enzymes in the regulation of cell proliferation, these results indicate that the expression of high levels of tyrosine kinase activity is not exclusively associated with proliferating cells.
我们检测了人和兔的血小板中pp60c-src的表达情况，pp60c-src是劳氏肉瘤病毒转化蛋白的正常细胞同源物。pp60c-src激酶活性通过以烯醇酶为底物的免疫复合物激酶测定法来确定，pp60c-src蛋白水平通过免疫印迹测定法来确定。与其他组织中的水平相比，血小板裂解物表达了高水平的pp60c-src特异性激酶活性和pp60c-src蛋白。pp60c-src还被发现是从血小板中分离出的膜在体外磷酸化的主要蛋白之一。在膜磷酸化反应中，除pp60c-src外的多种蛋白质也在酪氨酸上被磷酸化，磷酸酪氨酸约占膜中磷酸化的总磷酸氨基酸残基的80%。这些结果表明酪氨酸激酶是在分离的血小板膜中检测到的主要蛋白质磷酸化酶。尽管酪氨酸激酶活性与许多病毒癌基因产物和细胞生长激素受体的关联表明这些酶在细胞增殖调节中起作用，但这些结果表明高水平酪氨酸激酶活性的表达并非仅与增殖细胞相关。
