Alpha-conotoxins act on postsynaptic membranes, they bind to the nicotinic acetylcholine receptors (nAChR) and thus inhibit them. This globular toxin inhibits human alpha-7/CHRNA7 (IC(50)=0.3-10.1 nM), rat alpha-3-beta-2/CHRNA3-CHRNB2 (IC(50)=10.3 nM) and rat alpha-3-alpha-5-beta-2/CHRNA3-CHRNB5-CHRNB2 (IC(50)=31.2 nM). Expressed by the venom duct. The cysteine framework is I (CC-C-C). Alpha4/7 pattern. Amidation at Cys-17 plays a critical role, since a C-terminally carboxylated analog is 3-fold less potent at the alpha-7/CHRNA7 nAChR subtype and 3-fold more potent at the alpha-3-beta-2/CHRNA3-CHRNB2 subtype. Shows a weak inhibition of alpha-3-beta-4/CHRNA3-CHRNB4 nAChR and does not inhibit alpha-9-alpha-10/CHRNA9-CHRNA10, alpha-4-beta-2/CHRNA4-CHRNB2 and alpha-4-beta-4/CHRNA4-CHRNB4 nAChR. The synthetic ribbon toxin is much less potent that the globular toxin (IC(50)=41 nM compared to 0.3 nM). Belongs to the conotoxin A superfamily.