title: Crystal structure of the GTPase-activating domain of human p120GAP and implications for the interaction with Ras.
abstract: Ras-related GTP-binding proteins function as molecular switches which cycle between GTP-bound 'on'- and GDP-bound 'off'-states. GTP hydrolysis is the common timing mechanism that mediates the return from the 'on' to the 'off'-state. It is usually slow but can be accelerated by orders of magnitude upon interaction with GTPase-activating proteins (GAPs). In the case of Ras, a major regulator of cellular growth, point mutations are found in approximately 30% of human tumours which render the protein unable to hydrolyse GTP, even in the presence of Ras-GAPs. The first structure determination of a GTPase-activating protein reveals the catalytically active fragment of the Ras-specific p120GAP (ref. 2), GAP-334, as an elongated, exclusively helical protein which appears to represent a novel protein fold. The molecule consists of two domains, one of which contains all the residues conserved among different GAPs for Ras. From the location of conserved residues around a shallow groove in the central domain we can identify the site of interaction with Ras x GTP. This leads to a model for the interaction between Ras and GAP that satisfies numerous biochemical and genetic data on this important regulatory process.
authors.affiliation: Max-Planck-Institut für molekulare Physiologie, Dortmund, Germany.
authors.forename: K
authors.initials: K
authors.lastname: Scheffzek
authors.forename: A
authors.initials: A
authors.lastname: Lautwein
authors.forename: W
authors.initials: W
authors.lastname: Kabsch
authors.forename: M R
authors.initials: MR
authors.lastname: Ahmadian
authors.forename: A
authors.initials: A
authors.lastname: Wittinghofer
mesh_terms: D000595:Amino Acid Sequence; D002384:Catalysis; D018360:Crystallography, X-Ray; D020558:GTP Phosphohydrolases / Q000378:metabolism; D020690:GTPase-Activating Proteins; D006160:Guanosine Triphosphate / Q000378:metabolism; D006801:Humans; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009154:Mutation; D010446:Peptide Fragments / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D011487:Protein Conformation; D017510:Protein Folding; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D011506:Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D011994:Recombinant Proteins / Q000737:chemistry; D020703:ras GTPase-Activating Proteins; D018631:ras Proteins / Q000378:metabolism*
chemical_list: D020690:GTPase-Activating Proteins; D010446:Peptide Fragments; D011506:Proteins; D011994:Recombinant Proteins; D020703:ras GTPase-Activating Proteins; D006160:Guanosine Triphosphate; D020558:GTP Phosphohydrolases; D018631:ras Proteins