Abstract
The acetylcholine receptor (AcChR) protein isolated from Torpedo californica possesses two binding sites for α-bungarotoxin. Although chemical modification and ligand-binding experiments have suggested that the two toxin binding sites are dissimilar, the toxin associates to its two sites on AcChR at identical rates. Incubation of AcChR-enriched membranes with volatile anesthetics and aliphatic alcohols retards the rate of association of toxin to one of its two binding sites on the high-affinity conformer of the protein. Kinetic plots of toxin binding characteristic of a single bimolecular association to AcChR become biphasic after incubation with these organic perturbants. Therefore, anesthetics and aliphatic alcohols alter the tertiary structure of the high-affinity conformer as well as stabilizing it relative to the low-affinity conformer. The differential response of the two toxin binding sites to these organic perturbants provides additional evidence of the non-equivalence of the binding loci.
- Copyright © 1981 by The American Society for Pharmacology and Experimental Therapeutics
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