Open AccessCharacterization of the α‐Bungarotoxin Receptor in Chick‐Embryo Retina
Author(s) -
BETZ Heinrich
Publication year - 1981
Publication title -
european journal of biochemistry
Language(s) - English
Resource type - Journals
eISSN - 1432-1033
pISSN - 0014-2956
DOI - 10.1111/j.1432-1033.1981.tb06311.x
Subject(s) - acetylcholine receptor , nicotinic agonist , dissociation constant , chemistry , acetylcholine , cholinergic , torpedo , bungarotoxin , receptor , biophysics , agonist , nicotinic acetylcholine receptor , alpha 4 beta 2 nicotinic receptor , ganglion type nicotinic receptor , medicine , biochemistry , endocrinology , biology
Primary cultures and membranes fractions from chick embryo retina bind iodinated α‐bungarotoxin, a highly selective ligand for nicotinic acetylcholine receptors from skeletal muscle and fish electric organ. The binding is saturable with an equilibrium dissociation constant ( K d ) of 0.75 ± 0.09 nM. The pseudo‐first‐order rate constant ( k +1 ) for binding at 37°C is 1.76 × 105 M −1 s −1 , the dissociation rate constant ( k −1 ) at 37°C is 1.15 × 10 −1 s −1 . Nicotinic cholinergic ligands and local anaesthetics inhibit α‐bungarotoxin binding. In the case of carbamoylcholine, the inhibition of binding depends on the time of exposure to this cholinergic agonist. α‐Bungarotoxin has no effect on the carbamoylcholine‐induced stimulation in sodium permeability of cultured retinal neurons. On sucrose density gradients containing Triton X‐100. the toxin binding site sediments with an apparent sedimentation coefficient of 10.5–11 S. Detergent‐solubilized α‐bungarotoxin receptor crossreacts with antisera raised against nicotinic acetylcholine receptors from Torpedo marmorata . These results are interpreted as indicating that α‐bungarotoxin binds to retinal nicotinic acetylcholine receptors without affecting cholinergic receptor function.