大豆叶片质膜蛋白激酶的自身磷酸化反应

利用Ferrell和Martin（1991）设计的测定印迹在PVDF膜上的蛋白激酶活性方法研究大豆叶片质膜蛋白激酶自身磷酸化反应活性，结果表明：与Mg－ATP相比，Mn－ATP是更有效的57KD蛋白激酶自身磷酸化反应底物；钙离子可以促进该激酶的自身磷酸化反应活性，而且EGTA可以显著降低它在SDS电泳中的迁移率，说明57KD蛋白激酶为依赖于钙的蛋白激酶；预磷酸化反应实验证明57KD蛋白激酶具有多个自身磷酸化反应位点，其分子的自身磷酸化状态可调性暗示这一激酶可能具有重要的生理功能。

Study on Autophosphorylation of Soybean Leaf Plasma Membrane Protein Kinases

: Autophosphorylation of protein kinases is an important posttranslational modification which, in many cases, ignificantly modifies further catalyticactivity by the protein kinases. By using an autophosphorylation assay of proteinkinases that had been separated from other proteins by SDS-PAGE and blotted onto PVDF membranes (Ferrell and Martin 1991 ), combined with in vitro prephosphorylation of the samples with,unlabelled ATP, we studied the in vitro autophosphorylation characteristics of soybean primary leaf plasma membrane protein kinases and the POssible effect of autophosphorylation on enzyme activi ties.It was found that Mn-ATP was a more effective substrate than Mg-ATP for the autophosphorylation of the 57 kD protein kinase. EGTA can shift the mobility of this kinase by SDS-PAGE, combined with the observation that Ca2 stimulated its autophosphorylation activity, this result indicated that the 57 kD protein kinase was a calcitum-dependent protein Kinase . The autophosphorylation activity of the 57 kD CDPK can be regulated in vitro by prephosphorylation reaction, and these results mply that there are multiple sites on the molecule for autophosphorylation.