Functional properties of nicotinic acetylcholine receptor subunits expressed in various combinations

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 alpha-subunit with either the gamma- or the delta-subunit is a prerequisite for generating the conformation necessary for agonist binding. The acetylcholine receptor devoid of either the beta-, gamma- or delta-subunit exhibits weak channel activity.