title: Receptor activation of G proteins.
abstract: G proteins are a highly conserved family of membrane-associated proteins composed of alpha, beta, and gamma subunits. The alpha subunit, which is unique for each G protein, binds GDP or GTP. Receptors such as those for beta- and alpha-adrenergic catecholamines, muscarinic agonists, and the retinal photoreceptor rhodopsin, catalyze the exchange of GDP for GTP binding to the alpha subunit of a specific G protein. G alpha.GTP regulates appropriate effector enzymes such as adenylyl cyclase or the cyclic GMP phosphodiesterase. The beta gamma-subunit complex of G proteins is required for efficient receptor-catalyzed alpha subunit guanine nucleotide exchange and also functions as an attenuator of alpha subunit activation of effector enzymes. Recent elucidation of both receptor and G protein primary sequence has allowed structural predictions and new experimental approaches to study the mechanism of receptor-catalyzed G protein regulation of specific effector systems and the control of cell function including metabolism, secretion, and growth.
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D019204:GTP-Binding Proteins / Q000378:metabolism*; D006150:Guanine Nucleotides / Q000378:metabolism*; D006153:Guanosine Diphosphate / Q000378:metabolism*; D006160:Guanosine Triphosphate / Q000378:metabolism*; D006801:Humans; D008969:Molecular Sequence Data; D011941:Receptors, Adrenergic / Q000378:metabolism*; D011976:Receptors, Muscarinic / Q000378:metabolism*
chemical_list: D006150:Guanine Nucleotides; D011941:Receptors, Adrenergic; D011976:Receptors, Muscarinic; D006153:Guanosine Diphosphate; D006160:Guanosine Triphosphate; D019204:GTP-Binding Proteins