Interaction scheme of the binding of acetylcholine receptor with cobratoxin and erabutoxin.

Snake toxins bind to the periphery of acetylcholine receptor which overlaps with the agonist site, thus inhibiting the ion channel opening mechanism. It has been proposed (Stroud and Finer-Moore, 1985) that the residues lying between Cys 130 and Cys 142 of the alpha-subunit of the acetylcholine receptor participate in the binding of toxins. A three-dimensional model of acetylcholine with cobratoxin and erabutoxin is built based on the interaction scheme proposed by Smart et al. (1984). The differences in the hydrogen bonding schemes between the two complexes are discussed. The results show the effect of the conservative substitution (Asp/Glu) at position 42 in the toxins on the binding interactions.