[¹⁴C]Chloroacetylcholine as an Advantageous Affinity Label of the Acetylcholine Receptor

Abstract

The alkylating agent [¹⁴C]chloroacetylcholine perchlorate ([¹⁴C] ClACh) was synthesized and used for affinity labelling of the nicotinic acetylcholine receptor from Torpedo marmorata. Solubilized and affinity-purified receptor proteins were reduced and alkylated according to the bromoacetylcholine-method. Covalent binding of [¹⁴C] ClACh to the cholinergic receptor proved to be specific and saturable, and occurred exclusively to the α- subunit. Halogen substitution of acetylcholine by chlorine and insertion of a ¹⁴C-isotope instead of the widely used ³H resulted in favourable properties of the affinity label.