title: Ligand interactions with the acetylcholine receptor from Torpedo californica. Extensions of the allosteric model for cooperativity to half-of-site activity.
abstract: The solubilized acetylcholine receptor from Torpedo californica showed positive cooperativity in acetylcholine binding with a dissociation constant of 1.2 X 10(-8) M. Blockade of acetylcholine binding by nicotine was competitive; blockade by d-tubocurarine appeared to result from an allosteric interaction that altered half of the acetylcholine binding sites to a lower affinity form; decamethonium blockade displayed properties of competitive and allosteric inhibition suggesting less specificity for decamethonium binding than seen with either nicotine or d-tubocurarine. The d-tubocurarine inhibition data were evaluated by several possible models involving either differential competitive inhibition or allosteric inhibiton. The data were best described by the allosteric model.
mesh_terms: D000109:Acetylcholine / Q000378:metabolism; D000495:Allosteric Site; D000818:Animals; D003650:Decamethonium Compounds / Q000494:pharmacology; D005399:Fishes; D008024:Ligands; D008954:Models, Biological; D009538:Nicotine / Q000494:pharmacology; D011485:Protein Binding; D011950:Receptors, Cholinergic / Q000187:drug effects*; D014403:Tubocurarine / Q000494:pharmacology
chemical_list: D003650:Decamethonium Compounds; D008024:Ligands; D011950:Receptors, Cholinergic; D009538:Nicotine; D000109:Acetylcholine; D014403:Tubocurarine