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Inhibition of the ras p21 GTPase-activating protein-stimulated GTPase activity of c-Ha-ras p21 by smg p21 having the same putative effector domain as ras p21s. 1990

Y Hata, and A Kikuchi, and T Sasaki, and M D Schaber, and J B Gibbs, and Y Takai
Department of Biochemistry, Kobe University School of Medicine, Japan.

ras p21 GTPase-activating protein (GAP) has been proposed to interact with the putative effector domain of ras p21s, and smg p21, a ras p21-like guanine nucleotide binding protein (G protein), has been shown to have the same amino acid sequence as ras p21s in this region. In the present studies, we examined the effects of ras p21 GAP on the GTPase activity of smg p21 purified from human platelets, of smg p21 on the ras p21 GAP-stimulated GTPase activity of c-Ha-ras p21 purified from Escherichia coli, and of c-Ha-ras p21 on the smg p21 GAP1- or -2-stimulated GTPase activity of smg p21. ras p21 GAP stimulated the GTPase activity of c-Ha-ras p21 but not that of smg p21. The GTP-bound form of smg p21, however, inhibited the ras p21 GAP-stimulated GTPase activity of c-Ha-ras p21 in a dose-dependent manner. The half-maximum inhibition by smg p21 was obtained at 0.4 microM which was more potent than previously observed for ras p21 (2-200 microM). The GDP-bound form also inhibited the ras p21 GAP-stimulated GTPase activity of c-Ha-ras p21, but the efficiency was 40-50% that of the GTP-bound form. smg p21 GAP1 and -2 stimulated the GTPase activity of smg p21 but not that of c-Ha-ras p21. c-Ha-ras p21 did not inhibit the smg p21 GAP1- or -2-stimulated GTPase activity of smg p21. These results indicate that ras p21 GAP interacts with smg p21 without the subsequent stimulation of its GTPase activity.

UI MeSH Term Description Entries
D007700 Kinetics The rate dynamics in chemical or physical systems.
D010744 Phosphoric Monoester Hydrolases A group of hydrolases which catalyze the hydrolysis of monophosphoric esters with the production of one mole of orthophosphate. Phosphatase,Phosphatases,Phosphohydrolase,Phosphohydrolases,Phosphomonoesterase,Phosphomonoesterases,Phosphoric Monoester Hydrolase,Hydrolase, Phosphoric Monoester,Hydrolases, Phosphoric Monoester,Monoester Hydrolase, Phosphoric
D011506 Proteins Linear POLYPEPTIDES that are synthesized on RIBOSOMES and may be further modified, crosslinked, cleaved, or assembled into complex proteins with several subunits. The specific sequence of AMINO ACIDS determines the shape the polypeptide will take, during PROTEIN FOLDING, and the function of the protein. Gene Products, Protein,Gene Proteins,Protein,Protein Gene Products,Proteins, Gene
D011994 Recombinant Proteins Proteins prepared by recombinant DNA technology. Biosynthetic Protein,Biosynthetic Proteins,DNA Recombinant Proteins,Recombinant Protein,Proteins, Biosynthetic,Proteins, Recombinant DNA,DNA Proteins, Recombinant,Protein, Biosynthetic,Protein, Recombinant,Proteins, DNA Recombinant,Proteins, Recombinant,Recombinant DNA Proteins,Recombinant Proteins, DNA
D001792 Blood Platelets Non-nucleated disk-shaped cells formed in the megakaryocyte and found in the blood of all mammals. They are mainly involved in blood coagulation. Platelets,Thrombocytes,Blood Platelet,Platelet,Platelet, Blood,Platelets, Blood,Thrombocyte
D006801 Humans Members of the species Homo sapiens. Homo sapiens,Man (Taxonomy),Human,Man, Modern,Modern Man
D015689 Oncogene Protein p21(ras) Transforming protein encoded by ras oncogenes. Point mutations in the cellular ras gene (c-ras) can also result in a mutant p21 protein that can transform mammalian cells. Oncogene protein p21(ras) has been directly implicated in human neoplasms, perhaps accounting for as much as 15-20% of all human tumors. This enzyme was formerly listed as EC 3.6.1.47. p21(v-Ha-ras),p21(v-Ki-ras),ras Oncogene Protein p21,p21 Transforming Viral Protein,p21 v-H-ras,p21 v-Ha-ras,p21 v-Ki-ras,p21 v-ras,p21(v-H-ras),p21(v-K-ras),ras Oncogene Product p21,ras Oncogene p21 Product,p21 v H ras,p21 v Ha ras,p21 v Ki ras,p21 v ras,v-H-ras, p21,v-Ha-ras, p21,v-Ki-ras, p21,v-ras, p21
D019204 GTP-Binding Proteins Regulatory proteins that act as molecular switches. They control a wide range of biological processes including: receptor signaling, intracellular signal transduction pathways, and protein synthesis. Their activity is regulated by factors that control their ability to bind to and hydrolyze GTP to GDP. EC 3.6.1.-. G-Proteins,GTP-Regulatory Proteins,Guanine Nucleotide Regulatory Proteins,G-Protein,GTP-Binding Protein,GTP-Regulatory Protein,Guanine Nucleotide Coupling Protein,G Protein,G Proteins,GTP Binding Protein,GTP Binding Proteins,GTP Regulatory Protein,GTP Regulatory Proteins,Protein, GTP-Binding,Protein, GTP-Regulatory,Proteins, GTP-Binding,Proteins, GTP-Regulatory
D020558 GTP Phosphohydrolases Enzymes that hydrolyze GTP to GDP. EC 3.6.1.-. GTPase,GTPases,Guanosine Triphosphate Phosphohydrolases,Guanosinetriphosphatases,GTP Phosphohydrolase,Phosphohydrolase, GTP,Phosphohydrolases, GTP,Phosphohydrolases, Guanosine Triphosphate,Triphosphate Phosphohydrolases, Guanosine
D020690 GTPase-Activating Proteins Proteins that activate the GTPase of specific GTP-BINDING PROTEINS. GAP Proteins,GAP Protein,GTPase-Activating Protein,GTPase Activating Protein,GTPase Activating Proteins

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