title: The Rap-RapGAP complex: GTP hydrolysis without catalytic glutamine and arginine residues.
abstract: The GTP-binding protein Rap1 regulates integrin-mediated and other cell adhesion processes. Unlike most other Ras-related proteins, it contains a threonine in switch II instead of a glutamine (Gln61 in Ras), a residue crucial for the GTPase reaction of most G proteins. Furthermore, unlike most other GTPase-activating proteins (GAPs) for small G proteins, which supply a catalytically important Arg-finger, no arginine residue of RapGAP makes a significant contribution to the GTPase reaction of Rap1. For a detailed understanding of the reaction mechanism, we have solved the structure of Rap1 in complex with Rap1GAP. It shows that the Thr61 of Rap is away from the active site and that an invariant asparagine of RapGAPs, the Asn-thumb, takes over the role of the cis-glutamine of Ras, Rho or Ran. The structure and biochemical data allow to further explain the mechanism and to define the important role of a conserved tyrosine. The structure and biochemical data furthermore show that the RapGAP homologous region of the tumour suppressor Tuberin is sufficient for catalysis on Rheb.
authors.affiliation: Department of Structural Biology, Max-Planck-Institute of Molecular Physiology, Dortmund, Germany.
authors.forename: Andrea
authors.initials: A
authors.lastname: Scrima
authors.forename: Christoph
authors.initials: C
authors.lastname: Thomas
authors.forename: Delia
authors.initials: D
authors.lastname: Deaconescu
authors.forename: Alfred
authors.initials: A
authors.lastname: Wittinghofer
mesh_terms: D000595:Amino Acid Sequence; D001120:Arginine / Q000235:genetics / Q000378:metabolism; D001665:Binding Sites; D002384:Catalysis; D018360:Crystallography, X-Ray; D020690:GTPase-Activating Proteins / Q000737:chemistry* / Q000378:metabolism*; D005973:Glutamine / Q000235:genetics / Q000378:metabolism; D006160:Guanosine Triphosphate / Q000378:metabolism*; D006868:Hydrolysis; D008958:Models, Molecular; D008969:Molecular Sequence Data; D050505:Mutant Proteins / Q000737:chemistry / Q000378:metabolism; D011485:Protein Binding; D017433:Protein Structure, Secondary; D000077005:Tuberous Sclerosis Complex 2 Protein; D025521:Tumor Suppressor Proteins / Q000378:metabolism; D020827:rap1 GTP-Binding Proteins / Q000737:chemistry* / Q000378:metabolism*
chemical_list: D020690:GTPase-Activating Proteins; D050505:Mutant Proteins; D000077005:Tuberous Sclerosis Complex 2 Protein; D025521:Tumor Suppressor Proteins; D005973:Glutamine; D006160:Guanosine Triphosphate; D001120:Arginine; D020827:rap1 GTP-Binding Proteins