Fujioka H, Kikuchi A, Yoshida Y, Kuroda S, Takai Y
Department of Biochemistry, Kobe University School of Medicine, Japan.
Biochem Biophys Res Commun. 1990 May 16;168(3):1244-52. doi: 10.1016/0006-291x(90)91162-l.
We have recently purified from bovine brain cytosol a novel type of regulatory protein for smg p25A, named smg p25A GDP dissociation inhibitor (GDI), that regulates the GDP/GTP exchange reaction of smg p25A by inhibiting the dissociation of GDP from and thereby the subsequent binding of GTP to it. This smg p25A GDI is inactive for other ras p21/ras p21-like small GTP-binding proteins (G proteins) including c-Ha-ras p21, smg p21, rhoA p21 and rhoB p20. In human platelet membranes, smg p25A was not detected but a G protein with an apparent Mr value of 24,000 (24KG) was recognized by smg p25A GDI and the dissociation of GDP from and the binding of GTP to 24KG were inhibited by smg p25A GDI. The doses of smg p25A GDI necessary for these activities for both 24KG and smg p25A were the same. This 24KG was not recognized by an anti-smg p25A monoclonal antibody. The GDI activity for human platelet 24KG and smg p25A was detected in human platelet cytosol. This human platelet GDI was recognized by an anti-smg p25A GDI polyclonal antibody. These results indicate that there is a 24KG-24KG GDI system similar to a smg p25A-smg p25A GDI system in human platelets.
我们最近从牛脑细胞质中纯化出一种新型的smg p25A调节蛋白，名为smg p25A GDP解离抑制剂（GDI），它通过抑制GDP从smg p25A上解离，从而抑制随后GTP与之结合，来调节smg p25A的GDP / GTP交换反应。这种smg p25A GDI对其他ras p21 / ras p21样小GTP结合蛋白（G蛋白）无活性，包括c-Ha-ras p21、smg p21、rhoA p21和rhoB p20。在人血小板膜中，未检测到smg p25A，但一种表观分子量为24,000（24KG）的G蛋白可被smg p25A GDI识别，并且smg p25A GDI可抑制24KG上GDP的解离和GTP的结合。对于24KG和smg p25A，这些活性所需的smg p25A GDI剂量相同。这种24KG不能被抗smg p25A单克隆抗体识别。在人血小板细胞质中检测到了针对人血小板24KG和smg p25A的GDI活性。这种人血小板GDI可被抗smg p25A GDI多克隆抗体识别。这些结果表明，在人血小板中存在一个类似于smg p25A - smg p25A GDI系统的24KG - 24KG GDI系统。
