title: Copper ions and diamide induce a high affinity guanine-nucleotide-insensitive state for muscarinic agonists.
abstract: The binding capacity of [3H]-acetylcholine for muscarinic receptors of rat cerebral cortex membranes is increased in the presence of Cu2+ ions from 690 to 1320 fmol/mg protein with no significant change in affinity. Membranes treated with 50 microM Cu2+ and washed retain the increased binding capacity. Agonist binding in copper-treated membranes is insensitive to guanylylimidodiphosphate even at high concentrations (greater than 200 microM). Similar results were obtained when the sulfhydryl oxidizing agent, diamide (2 mM) was substituted for Cu2+ in the treatment of membranes. These data suggest the involvement of inter- or intra-molecular SH/S-S transitions in the interaction between the muscarinic receptor and a guanine nucleotide binding regulatory protein.
mesh_terms: D000818:Animals; D001391:Azo Compounds / Q000494:pharmacology*; D001667:Binding, Competitive; D002540:Cerebral Cortex / Q000378:metabolism; D003300:Copper / Q000494:pharmacology*; D003958:Diamide / Q000494:pharmacology*; D006150:Guanine Nucleotides / Q000494:pharmacology*; D006165:Guanylyl Imidodiphosphate / Q000494:pharmacology; D066298:In Vitro Techniques; D008297:Male; D008526:Medulla Oblongata / Q000378:metabolism; D011149:Pons / Q000378:metabolism; D051381:Rats; D011976:Receptors, Muscarinic / Q000187:drug effects / Q000378:metabolism*
chemical_list: D001391:Azo Compounds; D006150:Guanine Nucleotides; D011976:Receptors, Muscarinic; D003958:Diamide; D006165:Guanylyl Imidodiphosphate; D003300:Copper