Coupling of ras p21 signalling and GTP hydrolysis by GTPase activating proteins.
Ras p21 proteins cycle between inactive, GDP-bound forms and active GTP-bound forms. Hydrolysis of bound GTP to GDP is mediated by proteins referred to as GAPs, two forms of which have been described. The first, p120-GAP, contains regions of homologies with tyrosine kinase oncogenes, and interacts with tyrosine phosphoproteins as well as with ras proteins; p120-GAP may therefore connect signalling pathways that involve tyrosine kinase and ras p21 proteins. The second type of GAP is the product of the neurofibromatosis type 1 gene (NF1-GAP). This is a protein of 325,000 Da that is defective in patients with NF1; NF1-GAP is regulated by signalling lipids, and may serve to connect ras p21 with phospholipid second messenger systems. The significance of ras p21 interaction with distinct GAPs is discussed.
McCormick
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Cetus Corporation, Emeryville, California 94608.
D000818:Animals; D020690:GTPase-Activating Proteins; D006160:Guanosine Triphosphate / Q000378:metabolism; D006868:Hydrolysis; D008954:Models, Biological; D015689:Oncogene Protein p21(ras) / Q000378:metabolism*; D010982:Platelet-Derived Growth Factor / Q000378:metabolism; D011506:Proteins / Q000378:metabolism*; D011956:Receptors, Cell Surface / Q000378:metabolism; D017479:Receptors, Platelet-Derived Growth Factor; D020703:ras GTPase-Activating Proteins
D020690:GTPase-Activating Proteins; D010982:Platelet-Derived Growth Factor; D011506:Proteins; D011956:Receptors, Cell Surface; D020703:ras GTPase-Activating Proteins; D006160:Guanosine Triphosphate; D017479:Receptors, Platelet-Derived Growth Factor; D015689:Oncogene Protein p21(ras)