title: Crystal structure of the adenylyl cyclase activator Gsalpha.
abstract: The crystal structure of Gsalpha, the heterotrimeric G protein alpha subunit that stimulates adenylyl cyclase, was determined at 2.5 A in a complex with guanosine 5'-O-(3-thiotriphosphate) (GTPgammaS). Gsalpha is the prototypic member of a family of GTP-binding proteins that regulate the activities of effectors in a hormone-dependent manner. Comparison of the structure of Gsalpha.GTPgammaS with that of Gialpha.GTPgammaS suggests that their effector specificity is primarily dictated by the shape of the binding surface formed by the switch II helix and the alpha3-beta5 loop, despite the high sequence homology of these elements. In contrast, sequence divergence explains the inability of regulators of G protein signaling to stimulate the GTPase activity of Gsalpha. The betagamma binding surface of Gsalpha is largely conserved in sequence and structure to that of Gialpha, whereas differences in the surface formed by the carboxyl-terminal helix and the alpha4-beta6 loop may mediate receptor specificity.
authors.affiliation: Department of Pharmacology, The University of Texas Southwestern Medical Center, 5323 Harry Hines Boulevard, Dallas, TX 75235-9041, USA.
authors.forename: R K
authors.initials: RK
authors.lastname: Sunahara
authors.forename: J J
authors.initials: JJ
authors.lastname: Tesmer
authors.forename: A G
authors.initials: AG
authors.lastname: Gilman
authors.forename: S R
authors.initials: SR
authors.lastname: Sprang
mesh_terms: D000262:Adenylyl Cyclases / Q000737:chemistry / Q000378:metabolism*; D000595:Amino Acid Sequence; D001665:Binding Sites; D017124:Conserved Sequence; D003460:Crystallization; D018360:Crystallography, X-Ray; D019281:Dimerization; D004789:Enzyme Activation; D020558:GTP Phosphohydrolases / Q000378:metabolism; D019206:GTP-Binding Protein alpha Subunits, Gi-Go / Q000737:chemistry / Q000378:metabolism; D019205:GTP-Binding Protein alpha Subunits, Gs / Q000737:chemistry* / Q000378:metabolism; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000737:chemistry* / Q000378:metabolism; D006160:Guanosine Triphosphate / Q000378:metabolism; D006868:Hydrolysis; D008274:Magnesium / Q000378:metabolism; D008958:Models, Molecular; D008969:Molecular Sequence Data; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D015398:Signal Transduction
chemical_list: D016244:Guanosine 5'-O-(3-Thiotriphosphate); D006160:Guanosine Triphosphate; D020558:GTP Phosphohydrolases; D019206:GTP-Binding Protein alpha Subunits, Gi-Go; D019205:GTP-Binding Protein alpha Subunits, Gs; D000262:Adenylyl Cyclases; D008274:Magnesium