Sherrill J M, Kyte J
Department of Chemistry (0506), University of California at San Diego, La Jolla 92093-0506, USA.
Biochemistry. 1999 Mar 9;38(10):3106-11. doi: 10.1021/bi982276d.
The addition of epidermal growth factor (EGF) to epidermal growth factor receptor (EGF receptor) dissolved in a solution of the detergent Triton X-100 results in the activation of its protein tyrosine kinase. To investigate the importance of the sites for self-phosphorylation on the enzyme in this process, the kinetics of activation of a deletion mutant missing the last 195 amino acids of the protein, including all of the sites for self-phosphorylation, were followed by monitoring the initial velocity at which the enzyme catalyzes the phosphorylation of the exogenous substrate RRKGSTAENAEYLRV. The activation of the enzymatic activity of this deletion mutant of EGF receptor displays kinetics that are second-order with respect to the concentration of the enzyme as does wild-type EGF receptor. The second-order rate constant for its activation is 36 +/- 10 microM-1 min-1, which is only 3-fold greater than the second-order rate constant for the activation of wild-type EGF receptor under the same conditions (13 +/- 2 microM-1 min-1). These results suggest that the mechanism by which the protein tyrosine kinase of the deletion mutant is activated is the same as that for the activation of the wild-type receptor and that the sites of self-phosphorylation in the wild-type EGF receptor do not participate in the mechanism of activation of the enzyme.
将表皮生长因子（EGF）添加到溶解在去污剂Triton X - 100溶液中的表皮生长因子受体（EGF受体）中，会导致其蛋白酪氨酸激酶的激活。为了研究该过程中酶上自身磷酸化位点的重要性，通过监测酶催化外源底物RRKGSTAENAEYLRV磷酸化的初始速度，跟踪了缺失该蛋白最后195个氨基酸（包括所有自身磷酸化位点）的缺失突变体的激活动力学。该EGF受体缺失突变体的酶活性激活所呈现的动力学，与野生型EGF受体一样，对酶浓度呈二级反应。其激活的二级速率常数为36±10 μM⁻¹ min⁻¹，仅比相同条件下野生型EGF受体激活的二级速率常数（13±2 μM⁻¹ min⁻¹）大3倍。这些结果表明，缺失突变体的蛋白酪氨酸激酶被激活的机制与野生型受体激活的机制相同，并且野生型EGF受体中的自身磷酸化位点不参与酶的激活机制。
