title: Ras-mediated cleavage of a GTP analogue by a novel mechanism.
abstract: The small guanosine triphosphate (GTP) binding protein Ras is involved in many cellular signal transduction processes leading to cell growth, differentiation and apoptosis. Mutations in ras genes are found in a large number of human tumours. GTP hydrolysis, the process that normally leads to the transition of the Ras protein from the active (GTP-bound) form to the inactive (GDP-bound) form is impaired due to these oncogenic mutations. In contrast, the GTP analogue 3,4-diaminobenzophenone(DABP)-phosphoramidate-GTP, a substrate for GTP-binding proteins, enables switching to the inactive GDP form in both wild-type and oncogenic Ras. Here we show by HPLC, mass spectrometry and NMR spectroscopy that the mechanism of this DABP-GTPase reaction is different from the physiological GTPase reaction. The gamma-phosphate group is not attacked by a nucleophilic water molecule, but rather by the aromatic amino group of the analogue, which leads to the generation of a stable cyclic diamidate product. These findings have potential implications for the development of anti-Ras drugs.
authors.affiliation: Max-Planck-Institut für molekulare Physiologie, Abteilung Strukturelle Biologie, Otto-Hahn-Strasse 11, 44227 Dortmund, Germany.
authors.forename: R
authors.initials: R
authors.lastname: Gail
authors.forename: B
authors.initials: B
authors.lastname: Costisella
authors.forename: M R
authors.initials: MR
authors.lastname: Ahmadian
authors.forename: A
authors.initials: A
authors.lastname: Wittinghofer
mesh_terms: D001577:Benzophenones / Q000737:chemistry* / Q000378:metabolism; D006160:Guanosine Triphosphate / Q000031:analogs & derivatives* / Q000737:chemistry* / Q000378:metabolism; D007700:Kinetics; D019906:Nuclear Magnetic Resonance, Biomolecular; D018631:ras Proteins / Q000737:chemistry* / Q000378:metabolism
chemical_list: C109051:3,4-diaminobenzophenone-phosphonoamidate-GTP; D001577:Benzophenones; D006160:Guanosine Triphosphate; D018631:ras Proteins