Eckhart W, Hutchinson M A, Hunter T
Cell. 1979 Dec;18(4):925-33. doi: 10.1016/0092-8674(79)90205-8.
Polyoma T antigen immunoprecipitates contain a protein kinase-like activity which preferentially phosphorylates material of 50-60,000 daltons molecular weight. Phosphorylation is not diminished in extracts of polyoma tsA mutant-infected cells shifted to the nonpermissive temperature late in infection, conditions which inactivate the large T antigen. Phosphorylation is reduced or absent in cells infected with polyoma host range nontransforming (hr-t) mutants, which have defective small and medium T antigens. The major acceptor of phosphate is not the heavy chain of immunoglobulin, but appears to be the polyoma medium T antigen. The large T antigen is also phosphorylated, but usually to a lower specific activity. In terms of acid and alkali sensitivity and electrophoretic and chromatographic mobility in one and two dimensions, the phosphorylated residue behaves identically to phosphotyrosine and differently than phosphorylated serine, threonine, lysine and histidine.
多瘤病毒T抗原免疫沉淀物含有一种蛋白激酶样活性，它优先磷酸化分子量为50000 - 60000道尔顿的物质。在感染后期转移到非允许温度的多瘤病毒tsA突变体感染细胞的提取物中，磷酸化作用并未减弱，这种条件会使大T抗原失活。在感染多瘤病毒宿主范围非转化（hr - t）突变体的细胞中，磷酸化作用降低或不存在，这些突变体的小T抗原和中T抗原存在缺陷。磷酸盐的主要受体不是免疫球蛋白的重链，而似乎是多瘤病毒中T抗原。大T抗原也会被磷酸化，但通常比活性较低。就酸碱性敏感性以及一维和二维电泳及色谱迁移率而言，磷酸化残基的行为与磷酸酪氨酸相同，与磷酸化的丝氨酸、苏氨酸、赖氨酸和组氨酸不同。
