Proton magnetic resonance studies of cholinergic ligand binding to the 
acetylcholine receptor in its membrane environment

Miller, James; Witzemann, Veit; Quast, Ulrich; Raftery, Michael A.

doi:10.1073/pnas.76.8.3580

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Proton magnetic resonance studies of cholinergic ligand binding to the acetylcholine receptor in its membrane environment

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Witzemann, Veit
Department of Molecular Neurobiology, Max Planck Institute for Medical Research, Max Planck Society;
Working Group Witzemann / Koenen, Max Planck Institute for Medical Research, Max Planck Society;
Molecular anatomy of the neuromuscular junction, Max Planck Institute for Medical Research, Max Planck Society;
Department of Cell Physiology, Max Planck Institute for Medical Research, Max Planck Society;

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Citation

Miller, J., Witzemann, V., Quast, U., & Raftery, M. A. (1979). Proton magnetic resonance studies of cholinergic ligand binding to the acetylcholine receptor in its membrane environment. Proceedings of the National Academy of Sciences of the United States of America, 76(8), 3580-3584. doi:10.1073/pnas.76.8.3580.

Cite as: https://hdl.handle.net/21.11116/0000-0001-229A-B

Abstract

Proton magnetic resonance has been used to monitor binding of choline, a known partial agonist, to acetylcholine receptor-enriched membrane preparations from Torpedo californica electroplax. The interaction between choline and receptor led to a broadening of the resonance of the choline methyl groups and this effect was reversed by alpha-bungarotoxin, a quasi-irreversible antagonist of the acetylcholine receptor. From the concentration dependence of line broadening the equilibrium dissociation constant for choline was obtained (Kd = 190 +/- 65 microM). The temperature dependence of the parameters observed in the choline titrations gave an enthalpy of binding delta H less than 1.5 kcal/mol and allowed estimates for the dissociation rate constant of the receptor-choline complex (kdiss greater than 1.6 x 10(3) S(1) and the respective activation energy, Ea (Kdiss) approximately 5.5 kcal/mol. The association of other ligands with the membrane-bound receptor could also be studied by observing effects of varying concentrations of such ligands on the choline methyl group linewidth at a constant choline concentration.