Figure 5.

Diverse structures of peptides from different cone snails which inhibit the nicotinic acetylcholine receptor at the postsynaptic terminus of the neuromuscular junction. The first four compounds [α-Gi (Gray et al., 1981); α-Ei (Martinez et al., 1995); α-Sii (Ramilo et al., 1992); αA-Piva (Hopkins et al., 1995)] are all competitive antagonists of the receptor. The fifth peptide, Ψ-piiie (Shon et al., 1997a) acts at a different site on the receptor complex and is a noncompetitive antagonist. Note the lack of sequence similarity between all of these peptides which are all produced in the venom ducts of fish-hunting Conus species.  ^, free C-terminus; #, amidated e-terminus; O, hydroxyproline.