Alpha-conotoxins act on postsynaptic membranes, they bind to the nicotinic acetylcholine receptors (nAChR) and thus inhibit them. Expressed by the venom duct. The cysteine framework is I (CC-C-C). Alpha4/3 pattern. Occurs in 2 forms, Reg1b has a 4-hydroxyproline at Pro-6, Reg1c contains unmodified proline at Pro-6. Belongs to the conotoxin A superfamily.