Alpha-conotoxins act on postsynaptic membranes, they bind to the nicotinic acetylcholine receptors (nAChR) and thus inhibit them. This toxin has higher affinity for the fetal (alpha-1/beta-1/gamma/delta subunits) subtype (IC(50)=<5 nM) of the receptor than for the adult (alpha-1/beta-1/epsilon/delta) subtype (IC(50)=4000 nM). It blocks the elicited currents completely and dissociates very slowly from the fetal muscle receptor. Expressed by the venom duct. The cysteine framework is IV (CC-C-C-C-C). Contains 3 disulfide bonds (By similarity). They are not added, since framework IV presents two different connectivities (I-V, II-III, IV-VI and I-III, II-V, IV-VI). Belongs to the conotoxin A superfamily.