Meckling-Hansen K, Nelson R, Branton P, Pawson T
EMBO J. 1987 Mar;6(3):659-66. doi: 10.1002/j.1460-2075.1987.tb04805.x.
Site-directed mutagenesis of the Fujinami sarcoma virus (FSV) genome has suggested that Tyr 1073 of the P130gag--fps protein-tyrosine kinase is a regulatory site. To investigate directly the ability of tyrosine phosphorylation to affect P130gag--fps kinase activity, the phosphotyrosyl phosphatase inhibitor orthovanadate and partially purified phosphotyrosyl phosphatases were used to manipulate the stoichiometry of P130gag--fps phosphorylation. Phosphorylation of P130gag--fps at Tyr 1073 correlated with enhanced kinase activity. The thermolabile phosphorylation, kinase activity and transforming ability of P140gag--fps encoded by a temperature-sensitive (ts)FSV variant were restored at the non-permissive temperature for transformation by incubation of infected cells with orthovanadate. In this case tyrosine phosphorylation can apparently functionally reactivate a conditionally defective v-fps kinase activity. These data suggest that reversible autophosphorylation at a conserved tyrosine within the v-fps kinase domain is a positive regulator of enzymatic activity and biological function. Phenotypic suppression of the tsFSV genetic defect by orthovanadate emphasizes the potential importance of phosphotyrosyl phosphatases in antagonizing tyrosine kinase action. It is suggested that autophosphorylation may constitute a molecular switch by which some protein-tyrosine kinases are activated.
对 Fujinami 肉瘤病毒（FSV）基因组进行的定点诱变表明，P130gag--fps 蛋白酪氨酸激酶的 Tyr 1073 是一个调节位点。为了直接研究酪氨酸磷酸化影响 P130gag--fps 激酶活性的能力，使用磷酸酪氨酸磷酸酶抑制剂原钒酸盐和部分纯化的磷酸酪氨酸磷酸酶来控制 P130gag--fps 的磷酸化化学计量。P130gag--fps 在 Tyr 1073 处的磷酸化与增强的激酶活性相关。通过用原钒酸盐孵育感染细胞，由温度敏感（ts）FSV 变体编码的 P140gag--fps 的热不稳定磷酸化、激酶活性和转化能力在转化的非允许温度下得以恢复。在这种情况下，酪氨酸磷酸化显然可以在功能上重新激活有条件缺陷的 v-fps 激酶活性。这些数据表明，v-fps 激酶结构域内保守酪氨酸处的可逆自磷酸化是酶活性和生物学功能的正调节因子。原钒酸盐对 tsFSV 遗传缺陷的表型抑制强调了磷酸酪氨酸磷酸酶在拮抗酪氨酸激酶作用中的潜在重要性。有人提出自磷酸化可能构成一种分子开关，通过它一些蛋白酪氨酸激酶被激活。
