Alpha-conotoxins act on postsynaptic membranes, they bind to the nicotinic acetylcholine receptors (nAChR) and thus inhibit them. This toxin reversibly blocks alpha-3-beta-2/CHRNA3-CHRNB2 (IC(50)=3.1-5.1 nM), alpha-7/CHRNA7 (IC(50)=4.5-5.1 nM), and alpha-4-beta-2/CHRNA4-CHRNB2 (IC(50)=128.6-390 nM) nAChRs. Expressed by the venom duct. The cysteine framework is I (CC-C-C). Alpha4/7 pattern. Gamma-carboxyglutamation of Glu-48 seems to be not important for nAChR inhibition, since synthetic peptides without this modification do not show change in inhibition of alpha-7/CHRNA7 and alpha-3-beta-2/CHRNA3-CHRNB2 nAChR and show a 2.3-fold increase in inhibition of alpha-4-beta-2/CHRNA4-CHRNB2 nAChR. Hydroxylation of Pro-60 seems to be important for nAChR inhibition, since synthetic peptides without this modification show a small decrease in inhibition of alpha-7/CHRNA7 and alpha-3-beta-2/CHRNA3-CHRNB2 nAChR and a very important decrease in inhibition of alpha-4-beta-2/CHRNA4-CHRNB2 nAChR. An amidation of Cys-63 increases potency against alpha-7/CHRNA7 (2.6-fold) and alpha-3-beta-2/CHRNA3-CHRNB2 (2-fold) nAChR. On the other hand, the peptide has no more activity on alpha-4-beta-2/CHRNA4-CHRNB2 nAChR with an amidated Cys-63. The mutant [V62N] (V18N) shows a very important selectivity for alpha-4-beta-2/CHRNA4-CHRNB2 over alpha-3-beta-2/CHRNA3-CHRNB2 nAChR. This toxin does not inhibit neuronal alpha-3-beta-4/CHRNA3-CHRNB4 and alpha-4-beta-4/CHRNA4-CHRNB4 nAChR, and muscle alpha-1-beta-1-gamma-delta/CHRNA1-CHRNB1-CHRND nAChR. Belongs to the conotoxin A superfamily.