Uniquely selective inhibitor of the mammalian fetal neuromuscular nicotinic acetylcholine receptor

We have purified and characterized a novel conotoxin from the venom of Conus obscurus, which has the unique property of selectively and potently inhibiting the fetal form of the mammalian neuromuscular nicotinic acetylcholine receptor (nAChR) (α1β1γδ-subunits). Although this conotoxin, αA-conotoxin OIVB (αA-OIVB), is a high-affinity antagonist (IC50 of 56 nM) of the fetal muscle nAChR, it has >1800-fold lower affinity for the adult muscle nAChR (α1β1εδ-subunits) and virtually no inhibitory activity at a high concentration on various neuronal nAChRs (IC50 > 100 μM in all cases).