ABSTRACT
The nicotinic acetylcholine receptor (AChR) + plays a central role in post-synaptic neuromuscular transmission by mediating ion flux across the cell membrane in response to binding of acetylcholine. This regulatory activity is inhibited by binding to an α-neurotoxin or to some anti-AChR antibodies. The receptor is a pentamer composed of four subunits. Functional studies have focused mostly on the α-subunit because it is responsible for binding acetylcholine and α-neurotoxins. The primary structures of all four AChR subunits of Torpedo californica have been derived from the respective cDNA sequences. The structure of the human α-sbuunit has also been obtained from the sequence of the genomic DNA. From the primary structure of each subunit, it was possible to identify transmembrane hydrophobic regions and the extracellular part of the chain. For efficient binding of the toxin to receptor, it is expected that multi-region attachments must occur in which hydrogen bonds, hydrophobic and electrostatic interactions all contribute.
