title: Separate GTP binding and GTPase activating domains of a G alpha subunit.
abstract: Most members of the guanosine triphosphatase (GTPase) superfamily hydrolyze guanosine triphosphate (GTP) quite slowly unless stimulated by a GTPase activating protein or GAP. The alpha subunits (G alpha) of the heterotrimeric G proteins hydrolyze GTP much more rapidly and contain an approximately 120-residue insert not found in other GTPases. Interactions between a G alpha insert domain and a G alpha GTP-binding core domain, both expressed as recombinant proteins, show that the insert acts biochemically as a GAP. The results suggest a general mechanism for GAP-dependent hydrolysis of GTP by other GTPases.
authors.affiliation: Department of Pharmcology, University of California, San Francisco 94143.
authors.forename: D W
authors.initials: DW
authors.lastname: Markby
authors.forename: R
authors.initials: R
authors.lastname: Onrust
authors.forename: H R
authors.initials: HR
authors.lastname: Bourne
mesh_terms: D000262:Adenylyl Cyclases / Q000378:metabolism; D000595:Amino Acid Sequence; D000818:Animals; D002460:Cell Line; D005576:Colforsin / Q000494:pharmacology; D000242:Cyclic AMP / Q000378:metabolism; D020558:GTP Phosphohydrolases / Q000378:metabolism*; D019204:GTP-Binding Proteins / Q000737:chemistry / Q000378:metabolism*; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000378:metabolism / Q000494:pharmacology; D006160:Guanosine Triphosphate / Q000378:metabolism*; D006868:Hydrolysis; D007700:Kinetics; D008969:Molecular Sequence Data; D009154:Mutation; D011487:Protein Conformation
chemical_list: D005576:Colforsin; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D006160:Guanosine Triphosphate; D000242:Cyclic AMP; D020558:GTP Phosphohydrolases; D019204:GTP-Binding Proteins; D000262:Adenylyl Cyclases