Ueda T, Kikuchi A, Ohga N, Yamamoto J, Takai Y
Department of Biochemistry, Kobe University School of Medicine, Japan.
Biochem Biophys Res Commun. 1989 Mar 31;159(3):1411-9. doi: 10.1016/0006-291x(89)92267-5.
Two proteins stimulating the GTPase activity of the smg-21 GTP-binding protein (smg p21) having the same effector domain as the ras proteins (ras p21s) are partially purified from the cytosol fraction of human platelets. These proteins, designated as smg p21 GTPase activating protein (GAP) 1 and 2, do not stimulate the GTPase activity of c-Ha-ras p21. The GAP activity for c-Ha-ras p21 is also detected in the cytosol fraction of human platelets. smg p21 GAP1 and 2 are separated from c-Ha-ras p21 GAP by column chromatographies. The activity of smg p21 GAP1 and 2 is killed by tryptic digestion or heat boiling. The Mr values of smg p21 GAP1 and 2 are similar and are estimated to be 2.5-3.5 x 10(5) by gel filtration analysis. These results indicate that there are two GAPs for smg p21 in addition to a GAP for c-Ha-ras p21 in human platelets.
从人血小板的胞质溶胶部分中部分纯化出两种刺激smg - 21 GTP结合蛋白（smg p21）的GTP酶活性的蛋白质，它们具有与ras蛋白（ras p21s）相同的效应结构域。这些蛋白质，命名为smg p21 GTP酶激活蛋白（GAP）1和2，不刺激c - Ha - ras p21的GTP酶活性。在人血小板的胞质溶胶部分中也检测到了对c - Ha - ras p21的GAP活性。通过柱色谱法将smg p21 GAP1和2与c - Ha - ras p21 GAP分离。smg p21 GAP1和2的活性可被胰蛋白酶消化或加热煮沸灭活。通过凝胶过滤分析，smg p21 GAP1和2的Mr值相似，估计为2.5 - 3.5×10⁵。这些结果表明，除了人血小板中存在对c - Ha - ras p21的GAP外，还存在两种针对smg p21的GAP。
