A structural model for the ligand‐binding sites at the nicotinic acetylcholine receptor

The structural properties of a selected segment of the 4 polypeptide chains of the acetylcholine receptor from Torpedo californica have been compared by model building studies. The particular segment (residues 135–142) is identical for the β, γ and δ subunits but differs in one position from the otherwise identical α‐peptide. We conclude that the exchange of a tryptophanyl by a glutaminyl residue may produce a sufficiently different folding and charge pattern to provide for the specific binding of cholinergic ligands to the α‐peptide.