Open AccessInterconversion between Different States of Affinity for Acetylcholine of the Cholinergic Receptor Protein from Torpedo marmorata
Author(s) -
SUGIYAMA Hiroyuki,
CHANGEUX JeanPierre
Publication year - 1975
Publication title -
european journal of biochemistry
Language(s) - English
Resource type - Journals
eISSN - 1432-1033
pISSN - 0014-2956
DOI - 10.1111/j.1432-1033.1975.tb02188.x
Subject(s) - torpedo , affinity chromatography , acetylcholine receptor , chemistry , acetylcholine , receptor , affinity labeling , chromatography , population , cholinergic , sodium , binding site , biochemistry , biology , enzyme , endocrinology , demography , organic chemistry , sociology
In receptor‐rich membrane fragments from Torpedo , acetylcholine binds, in the presence of 70 μM Tetram, to a homogeneous population of high‐affinity sites with K d = (3.4 ± 0.8) × 10 −8 M. Dissolution of these membrane fragments by sodium cholate causes a decrease of affinity associated with the appearance of medium‐affinity ( K d ∼ 10 −7 M) and low‐affinity ( K d ≥ 10 −6 M) sites. Dissolution by neutral detergents Triton X‐100 or Emulphogene preserves the high affinity of the acetylcholine binding sites. In all the soluble states of the receptor protein, Ca 2+ ions and local anaesthetics no longer enhance the affinity for acetylcholine. Elimination of sodium cholate by dilution leads to the reassociation of the receptor protein, the recovery of high‐affinity sites and the control by Ca 2+ ions and local anaesthetics. Purification by affinity chromatography of the receptor protein in Triton X‐100 is accompanied by a conversion of a majority of the acetylcholine sites into their state of low affinity. High‐affinity sites can no longer be recovered by detergent dilution from these low‐affinity ones.