Alpha-conotoxins act on postsynaptic membranes, they bind to the nicotinic acetylcholine receptors (nAChR) and thus inhibit them. This toxin blocks the fetal muscle subtype (alpha-1/beta-1/gamma/delta subunits) (IC(50)=66 nM) with 1500/2000-fold greater affinity than the adult (alpha-1/beta-1/epsilon/delta) subtype (IC(50)=96000 nM). It blocks the currents completely and dissociates rapidly from the fetal muscle receptor. Has no inhibitory activity on various neuronal nAChRs. This toxin causes a reversible paralysis upon injection into gold fish. Expressed by the venom duct. The cysteine framework is IV (CC-C-C-C-C). Belongs to the conotoxin A superfamily.