Courtneidge S A, Heber A
Cell. 1987 Sep 25;50(7):1031-7. doi: 10.1016/0092-8674(87)90169-3.
It has previously been shown that a proportion of middle T antigen molecules exist in a stable complex with pp60c-src. Here we show that there appears to be a third component to the complex, a protein of molecular mass 81 kd (p81). p81 was phosphorylated exclusively on tyrosine residues in kinase assays performed using immunoprecipitates from polyoma virus-transformed cells and antibodies to both middle T and pp60c-src, and was also detected when immunoprecipitates were made from lysates of 32P-labeled cells. p81 was bound to middle T and pp60c-src in cell lines containing transforming mutants of middle T, but not (in phosphorylated form) to all nontransforming mutants. A parallel investigation of phosphatidylinositol kinase activity in immune complexes containing these middle T mutants revealed a complete coincidence between the presence of p81 and phosphatidylinositol kinase activity. We therefore suggest that p81 is a phosphatidylinositol kinase.
先前的研究表明，一定比例的中T抗原分子与pp60c-src形成稳定复合物。在此我们发现，该复合物似乎还有第三种成分，一种分子量为81kd的蛋白质（p81）。在用多瘤病毒转化细胞的免疫沉淀物以及针对中T和pp60c-src的抗体进行的激酶分析中，p81仅在酪氨酸残基上被磷酸化，并且当从32P标记细胞的裂解物中制备免疫沉淀物时也能检测到它。在含有中T转化突变体的细胞系中，p81与中T和pp60c-src结合，但（以磷酸化形式）并非与所有非转化突变体结合。对含有这些中T突变体的免疫复合物中磷脂酰肌醇激酶活性的平行研究表明，p81的存在与磷脂酰肌醇激酶活性完全一致。因此我们认为p81是一种磷脂酰肌醇激酶。
