Research Article

The Ras-RasGAP Complex: Structural Basis for GTPase Activation and Its Loss in Oncogenic Ras Mutants

Science  18 Jul 1997:
Vol. 277, Issue 5324, pp. 333-339
DOI: 10.1126/science.277.5324.333

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Abstract

The three-dimensional structure of the complex between human H-Ras bound to guanosine diphosphate and the guanosine triphosphatase (GTPase)–activating domain of the human GTPase-activating protein p120GAP (GAP-334) in the presence of aluminum fluoride was solved at a resolution of 2.5 angstroms. The structure shows the partly hydrophilic and partly hydrophobic nature of the communication between the two molecules, which explains the sensitivity of the interaction toward both salts and lipids. An arginine side chain (arginine-789) of GAP-334 is supplied into the active site of Ras to neutralize developing charges in the transition state. The switch II region of Ras is stabilized by GAP-334, thus allowing glutamine-61 of Ras, mutation of which activates the oncogenic potential, to participate in catalysis. The structural arrangement in the active site is consistent with a mostly associative mechanism of phosphoryl transfer and provides an explanation for the activation of Ras by glycine-12 and glutamine-61 mutations. Glycine-12 in the transition state mimic is within van der Waals distance of both arginine-789 of GAP-334 and glutamine-61 of Ras, and even its mutation to alanine would disturb the arrangements of residues in the transition state.

  • * Present address: Heinrich Pette Institut für experimentelle Virologie und Immunologie an der Universität Hamburg, Martinistrasse 52, 20251 Hamburg, Germany.

  • Present address: Chester Beatty Laboratories, Fulham Road, London SW3 6JB, England.

  • To whom correspondence should be addressed. E-mail: Alfred.Wittinghofer{at}mpi-dortmund.mpg.de

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