α-Conotoxin GI, a 13-residue peptide originally isolated from the venom of the fish-hunting cone snail Conus geographus, acts as a competitive antagonist for the muscle-type nicotinic acetylcholine receptor (nAChR) with excellent selectivity for α/δ receptor subunit binding over α/γ.
[1] Knuhtsen A, et al. Chem. Sci., 2019, 10, 1671-1676.