Reaction of (3H)meproadifen mustard with membrane-bound Torpedo acetylcholine receptor

Journal Article · Wed Oct 15 00:00:00 EDT 1986 · J. Biol. Chem.; (United States)

OSTI ID:7022581

Dreyer, E B; Hasan, F; Cohen, S G; Cohen, J B

The Torpedo nicotinic acetylcholine receptor (AChR) contains a binding site for aromatic amine noncompetitive antagonists that is distinct from the binding site for agonists and competitive antagonists. To characterize the location and function of this allosteric antagonist site, an alkylating analog of meproadifen has been synthesized, 2-(chloroethylmethylamino)-ethyl-2, 2-diphenylpentanoate HCl (meproadifen mustard). Reaction of (/sup 3/H)meproadifen mustard with AChR-rich membrane suspensions resulted in specific incorporation of label predominantly into the AChR alpha-subunit with minor incorporation into the beta-subunit. Specific labeling required the presence of high concentration of agonist and was inhibited by reversible noncompetitive antagonists including proadifen, meproadifen, perhydrohistrionicotoxin (HTX), and tetracaine when present at concentrations consistent with the binding affinity of these compounds for the allosteric antagonist site. No specific alkylation of the AChR alpha-subunit was detected in the absence of agonist, or in the presence of the partial agonist phenyltrimethylammonium or the competitive antagonists, d-tubocurarine, gallamine triethiodide, or decamethonium. Reaction with 35 microM meproadifen mustard for 70 min in the presence of carbamylcholine produced no alteration in the concentration of (/sup 3/H)ACh-binding sites, but decreased by 38 +/- 4% the number of allosteric antagonist sites as measured by (/sup 3/H)HTX binding. This decrease was not observed when the alkylation reaction was blocked by the presence of HTX. These results lead us to conclude that meproadifen mustard alkylates the allosteric antagonist site in the Torpedo AChR and that part of that site is associated with the AChR alpha-subunit.

• Research Organization: Washington Univ. School of Medicine, St. Louis, MO
• OSTI ID: 7022581
• Journal Information: J. Biol. Chem.; (United States), Journal Name: J. Biol. Chem.; (United States) Vol. 29; ISSN JBCHA
• Country of Publication: United States
• Language: English

Related Subjects

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560300* -- Chemicals Metabolism & Toxicology
59 BASIC BIOLOGICAL SCIENCES
63 RADIATION, THERMAL, AND OTHER ENVIRON. POLLUTANT EFFECTS ON LIVING ORGS. AND BIOL. MAT.
ACETYLCHOLINE
ALKYLATING AGENTS
ALKYLATION
AMINES
AMMONIUM COMPOUNDS
AUTONOMIC NERVOUS SYSTEM AGENTS
BIOCHEMICAL REACTION KINETICS
CHEMICAL REACTIONS
DRUGS
ESTERS
KINETICS
LABELLED COMPOUNDS
MEMBRANE PROTEINS
NEUROREGULATORS
ORGANIC COMPOUNDS
PARASYMPATHOMIMETICS
PROTEINS
QUATERNARY COMPOUNDS
REACTION KINETICS
RECEPTORS
TRITIUM COMPOUNDS