The four kinds of subunits of the Torpedo californica nicotinic acetylcholine receptor have been produced in various combinations by injecting Xenopus oocytes with the corresponding subunit-specific mRNAs synthesized by transcription in vitro of the cloned cDNAs. Functional analysis suggests that association of the α-subunit with either the γ- or the δ-subunit is a prerequisite for generating the conformation necessary for agonist binding. The acetylcholine receptor devoid of either the β-, γ- or δ-subunit exhibits weak channel activity.
