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)=0.51 nM) with 600-fold greater affinity than the adult subtype (IC(50)=310 nM). It blocks the elicited currents completely and it dissociates very slowly from the fetal muscle receptor. This toxin causes an apparently irreversible paralysis upon intramuscular injection into gold fish. Expressed by the venom duct. The cysteine framework is IV (CC-C-C-C-C). The cysteine framework differs from the previously characterized alpha-A conotoxins. It also differs in its disulfide bonding. It is why authors (PubMed:15246771) propose the novel nomenclature Alpha-A(1-3) conotoxin OIVA. Belongs to the conotoxin A superfamily.