title: [The high affinity binding site for chlorpromazine is present only as a single copy per cholinergic receptor molecule and is shared by four polypeptide chains].
abstract: 3H chlorpromazine binds to acetylcholine receptor-rich membrane fragments prepared from Torpedo marmorata electric organ in three different manners: (1) at the level of high affinity sites from which it is displaced by perhydrohistrionicotoxin, (2) at the level of low affinity sites insensitive to this toxin, and (3) in a non saturable manner to a presumably lipidic phase. Binding of chlorpromazine to the first two categories of sites independently stabilizes the "desensitized" high affinity state of the receptor for cholinergic agonists. There exists one high affinity site per two snake alpha-toxin sites, thus per 250,000 daltons light form of the receptor. Under the conditions of 3H chlorpromazine high affinity binding, ultraviolet irradiation results in the covalent incorporation of this ligand to the four chains of the receptor.
mesh_terms: D000818:Animals; D002462:Cell Membrane / Q000378:metabolism; D002746:Chlorpromazine / Q000378:metabolism*; D004557:Electric Organ / Q000378:metabolism*; D007700:Kinetics; D046911:Macromolecular Substances; D008970:Molecular Weight; D011954:Receptors, Dopamine / Q000378:metabolism*; D014101:Torpedo
chemical_list: D046911:Macromolecular Substances; D011954:Receptors, Dopamine; C035323:chlorpromazine receptor; D002746:Chlorpromazine
vernacular_title: Le site de liaison de haute affinité de la chlorpromazine n'est présent qu'à un seul exemplaire par molécule de récepteur cholinergique et est commun aux quatre chaînes polypeptidiques.