In Vitro Biosynthesis of the Subunits of Acetylcholine Receptor

The acetylcholine receptor (AChR) of electric ray and eel is one of the few neurotransmitter receptors to be isolated and extensively characterized. It occupies a unique position in the catalogue of membrane proteins thus far purified, in that it is the only such protein that exhibits both a receptor and an ionophore activity. Located in the post-synaptic plasma membranes of Torpedo electric organ, the AChR is an oligomer of four non-identical subunits. The actual organization of these four polypeptides in the lipid bilayer, and their mechanism of functional interaction, however, is still unknown. The biosynthetic pathway of this molecular complex is an important aspect of the formation and maintenance of neuromuscular junctions. It is, furthermore, a potential paradigm for the manner in which other multi-subunit integral membrane proteins are assembled and transported to the plasmalemma.