Background: The nicotinic acetylcholine receptor controls electrical signaling between nerve and muscle cells by opening and closing a gated, membrane-spanning pore. The gate is a constricting hydrophobic girdle at the middle of the lipid bi-layer, formed by weak interactions between neighboring inner helices. When acetylcholine enters the ligand-binding domain, it triggers rotations of the protein chains on opposite sides of the entrance to the pore (1). The widespread distribution of the beta subunit suggests it may serve as a common subunit in different AChR combinations in various brain regions. Regulation of the expression of beta subunit appears to be relatively unrestrained, with an apparent excess of protein synthesized in the cytoplasm relative to that which ultimately arrives at functional targets in the plasma membrane (2).