title: Photoaffinity labeling of two rat liver plasma membrane proteins with [32P]gamma-azidoanilido GTP in response to vasopressin. Immunologic identification as alpha subunits of the Gq class of G proteins.
abstract: Two proteins have been identified in rat liver plasma membranes that bind a photoreactive GTP analogue, [32P]gamma-azidoanilido GTP, in response to incubation with the Ca(2+)-mobilizing agonist, vasopressin. The labeled proteins possess apparent molecular masses of 42 and 43 kDa. Their labeling requires Mg2+ and can be inhibited by GTP, its analogues, and GDP but not by other nucleotides. Vasopressin-stimulated labeling is attenuated by a V1 receptor-selective antagonist. The concentration of vasopressin required to stimulate labeling is in the same range (EC50 = 4 nM) as that required for activation of GTPase and phosphoinositide-specific phospholipase C activities in liver plasma membranes. Immunodetection and immunoprecipitation of the [32P]gamma-azidoanilido GTP-labeled 42- and 43-kDa proteins with antisera raised against peptide sequences in alpha q indicate that these proteins are members of the recently described Gq class of G proteins.
authors.affiliation: Department of Pharmacology, Vanderbilt University School of Medicine, Nashville, Tennessee 37232-0295.
authors.forename: R L
authors.initials: RL
authors.lastname: Wange
authors.forename: A V
authors.initials: AV
authors.lastname: Smrcka
authors.forename: P C
authors.initials: PC
authors.lastname: Sternweis
authors.forename: J H
authors.initials: JH
authors.lastname: Exton
mesh_terms: D000345:Affinity Labels; D000818:Animals; D001386:Azides / Q000737:chemistry*; D015153:Blotting, Western; D002118:Calcium / Q000378:metabolism; D004789:Enzyme Activation; D020558:GTP Phosphohydrolases / Q000378:metabolism; D019204:GTP-Binding Proteins / Q000378:metabolism*; D006160:Guanosine Triphosphate / Q000031:analogs & derivatives* / Q000737:chemistry; D008099:Liver / Q000187:drug effects* / Q000378:metabolism; D008297:Male; D008565:Membrane Proteins / Q000378:metabolism*; D043265:Phosphatidylinositol Diacylglycerol-Lyase; D010727:Phosphoric Diester Hydrolases / Q000378:metabolism*; D010777:Photochemistry; D011233:Precipitin Tests; D051381:Rats; D011919:Rats, Inbred Strains; D011945:Receptors, Angiotensin / Q000187:drug effects; D017483:Receptors, Vasopressin; D010738:Type C Phospholipases / Q000378:metabolism; D014667:Vasopressins / Q000494:pharmacology*
chemical_list: D000345:Affinity Labels; D001386:Azides; D008565:Membrane Proteins; D011945:Receptors, Angiotensin; D017483:Receptors, Vasopressin; D014667:Vasopressins; C031907:GTP gamma-4-azidoanilide; D006160:Guanosine Triphosphate; D010727:Phosphoric Diester Hydrolases; D010738:Type C Phospholipases; D020558:GTP Phosphohydrolases; D019204:GTP-Binding Proteins; D043265:Phosphatidylinositol Diacylglycerol-Lyase; D002118:Calcium