Acetylcholine receptor. Responses to drug binding.

Abstract

We have studied the interaction of nicotinic acetylcholine receptor, purified from the electric organ of Ebctrophorus electricus, with cobra cu-neurotoxin and with small cholinergic ligands.1.The neurotoxin-receptor interaction is noteworthy for very slow rates of association and dissociation, the forward second order rate constant being k, = (7.6 i 2.1) X lo6 M-' min-I.2. The formation of neurotoxin .receptor complexes proceeds from a single homogeneous population of receptor sites (R,) which appear to be paired; the association rate for both paired sites is the same.Saturation of one member of a pair with neurotoxin results in the formation of a single type of complex, CRT)*, of high affinity and low rate of dissociation (k, = (1.2+ 0.5) X 10m4 min-': k2