Weinmaster G A, Middlemas D S, Hunter T
Molecular Biology and Virology Laboratory, Salk Institute, San Diego, California 92138.
J Virol. 1988 Jun;62(6):2016-25. doi: 10.1128/JVI.62.6.2016-2025.1988.
Phosphorylation of the major autophosphorylation site (Tyr-1073) within Fujinami sarcoma virus P130gag-fps activates both the intrinsic protein-tyrosine kinase activity and transforming potential of the protein. In this report, a second site of autophosphorylation Tyr-836 was identified. This tyrosine residue is found within a noncatalytic domain (SH2) of P130gag-fps that is required for full protein-kinase activity in both rat and chicken cells. Autophosphorylation of this tyrosine residue implies that the SH2 region lies near the active site in the catalytic domain in the native protein and thus possibly regulates its enzymatic activity. Four mutations have occurred within the SH2 domain between the c-fps and v-fps proteins. Tyr-836 is one of these changes, being a Cys in c-fps. Site-directed mutagenesis was used to investigate the function of this autophosphorylation site. Substitution of Tyr-836 with a Phe had no apparent effect on the transforming ability or protein-tyrosine kinase activity of P130gag-fps in rat-2 cells. Mutagenesis of both autophosphorylation sites (Tyr-1073 and Tyr-836) did not reveal any cooperation between these two phosphorylation sites. The implications of the changes within the SH2 region for v-fps function and activation of the c-fps oncogenic potential are discussed.
藤浪肉瘤病毒P130gag - fps内主要自磷酸化位点（酪氨酸-1073）的磷酸化激活了该蛋白的内在蛋白酪氨酸激酶活性及其转化潜能。在本报告中，鉴定出了第二个自磷酸化位点——酪氨酸-836。该酪氨酸残基位于P130gag - fps的一个非催化结构域（SH2）内，在大鼠和鸡细胞中，该结构域是蛋白激酶充分发挥活性所必需的。该酪氨酸残基的自磷酸化表明，在天然蛋白中，SH2区域位于催化结构域的活性位点附近，因此可能调节其酶活性。在c - fps和v - fps蛋白之间的SH2结构域内发生了四处突变。酪氨酸-836就是其中之一，在c - fps中它是一个半胱氨酸。利用定点诱变研究了该自磷酸化位点的功能。将酪氨酸-836替换为苯丙氨酸对P130gag - fps在大鼠-2细胞中的转化能力或蛋白酪氨酸激酶活性没有明显影响。对两个自磷酸化位点（酪氨酸-1073和酪氨酸-836）进行诱变并未揭示这两个磷酸化位点之间存在任何协同作用。文中讨论了SH2区域内的变化对v - fps功能及c - fps致癌潜能激活的影响。
