Structure of the high-affinity binding site for noncompetitive blockers of the acetylcholine receptor: (/sup 3/H)chlorpromazine labels homologous residues in the. beta. and delta chains
The membrane-bound acetylcholine receptor from Torpedo marmorata was photolabeled by the noncompetitive channel blocker (/sup 3/H)chlorpromazine under equilibrium conditions in the presence of the agonist carbamoylcholine. The amount of radioactivity incorporated into all subunits was reduced by addition of phencyclidine, a specific ligand for the high-affinity site for noncompetitive blockers. The labeled ..beta.. chain was purified and digested with trypsin or CNBr, and the resulting fragments were fractionated by high-performance liquid chromatography. Sequence analysis resulted in the identification of Ser-254 and Leu-257 as residues labeled by (/sup 3/H)chlorpromazine in a phencyclidine-sensitive manner. These residues are located in the hydrophobic and potentially transmembrane segment M II of the ..beta.. chain, a region homologous to that containing the chlorpromazine-labeled Ser-262 in the delta chain. These results show that homologous regions of different receptor subunits contribute to the unique high-affinity site for noncompetitive blockers, a finding consistent with the location of this site on the axis of symmetry of the receptor molecule.
- Research Organization:
- Institut Pasteur, Paris, France
- OSTI ID:
- 5630023
- Journal Information:
- Biochemistry; (United States), Vol. 26:9
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
RECEPTORS
MOLECULAR STRUCTURE
TRITIUM COMPOUNDS
UPTAKE
ACETYLCHOLINE
AMINO ACID SEQUENCE
CHLORPROMAZINE
FISHES
LIQUID COLUMN CHROMATOGRAPHY
PROTEINS
PURIFICATION
AMINES
AMMONIUM COMPOUNDS
ANIMALS
AQUATIC ORGANISMS
AUTONOMIC NERVOUS SYSTEM AGENTS
AZINES
CENTRAL NERVOUS SYSTEM AGENTS
CENTRAL NERVOUS SYSTEM DEPRESSANTS
CHROMATOGRAPHY
DRUGS
ESTERS
HETEROCYCLIC COMPOUNDS
HYPNOTICS AND SEDATIVES
LABELLED COMPOUNDS
MEMBRANE PROTEINS
NEUROREGULATORS
ORGANIC CHLORINE COMPOUNDS
ORGANIC COMPOUNDS
ORGANIC HALOGEN COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
ORGANIC SULFUR COMPOUNDS
PARASYMPATHOMIMETICS
PHENOTHIAZINES
PSYCHOTROPIC DRUGS
QUATERNARY COMPOUNDS
SEPARATION PROCESSES
TRANQUILIZERS
VERTEBRATES
550201* - Biochemistry- Tracer Techniques