Alpha-conotoxins bind to the nicotinic acetylcholine receptors (nAChR) and inhibit them. This peptide potently blocks numerous mammalian nAChR subtypes: alpha-6/alpha-3-beta-2 (CHRNA6/CHRNA3-CHRNB2) (IC(50)=0.258 nM) > alpha-6/alpha-3-beta-4 (CHRNA6/CHRNA3-CHRNB4) (IC(50)=1.54 nM) > alpha-3-beta-2 (CHRNA3-CHRNB2) (IC(50)=5.72 nM) > alpha-3-beta-4 (CHRNA3-CHRNB4)(IC(50)=27.7 nM) > alpha-4-beta-4 (CHRNA4-CHRNB4) (IC(50)=69.9 nM) > alpha-2-beta-4 (CHRNA2-CHRNB4) (IC(50)=121 nM) > alpha-7 (CHRNA7) (IC(50)=272 nM) > alpha-2-beta-2 (CHRNA2-CHRNB2) (IC(50)=800 nM) (PubMed:15520009). Recovery from toxin block is markedly slower for beta-4 versus beta-2 subunit-containing nAChRs (PubMed:15520009, PubMed:16964981). Residues Thr-83, Val-135 and Phe-143 in the rat beta-2 subunit and Lys-81, Ile-133 and Gln-141 in the rat beta-4 subunit are critical to off-rate differences (PubMed:16964981). Thus, this toxin represents a novel probe for distinguishing between beta-2 and beta-4 subunit-containing nAChRs (PubMed:15520009, PubMed:16964981). Also exhibits inhibition of D.melanogaster alpha-7 nAChRs (PubMed:25466886). Expressed by the venom duct. The cysteine framework is I (CC-C-C). Alpha4/4 pattern. The native globular disulfide connectivity of this toxin displays multiple conformations in solution. In contrast, the non-native ribbon isomer has a well-defined conformation. This ribbon isomer is inactive on alpha-3-beta-2 (CHRNA3-CHRNB2) and alpha-3-beta-4 (CHRNA3-CHRNB4)nAChR. Post-translational modification of Pro-49 into hydroxyproline [P49O] induces a 2800-fold decrease in inhibition of alpha-6/alpha-3-beta-2-beta-3 (CHRNA6/CHRNA3-CHRNB2-CHRNB3) and 6-fold decrease in inhibition of alpha-6/alpha-3-beta-4 (CHRNA6/CHRNA3-CHRNB4). Post-translational modification of Pro-49 into hydroxyproline [P49O] associated with the mutation [T48A] induces a preferential inhibition of beta-4 subunit-containing nAChRs (over beta-2). On mouse/rat subunits, this mutant induces potent blocks of alpha-6/alpha-3-beta-4 (CHRNA6/CHRNA3-CHRNB4), moderate block of alpha-3-beta-4 (CHRNA3-CHRNB4), weak block of alpha-2-beta-4 (CHRNA2-CHRNB4) nAChRs and no activity on alpha-2-beta-2 (CHRNA2-CHRNB2), alpha-3-beta-2 (CHRNA3-CHRNB2), alpha-4-beta-2 (CHRNA4-CHRNB2), alpha-4-beta-4 (CHRNA4-CHRNB4), alpha-6/alpha-3-beta-2-beta-3 (CHRNA6/CHRNA3-CHRNB2-CHRNB3), alpha-7 (CHRNA7) and alpha-9-alpha-10 (CHRNA9-CHRNA10) and alpha-1-beta-1-delta-epsilon (CHRNA1-CHRNB1-CHRND-CHRNE) nAChRs (PubMed:20739611). On human subunits, this mutant induces inhibitions on alpha-6/alpha-3-beta-4 (CHRNA6/CHRNA3-CHRNB4) (IC(50)=7.4 nM), beta-4-alpha-3-beta-4-alpha-3-alpha-5 (CHRNB4-CHRNA3-CHRNB4-CHRNA3-CHRNA5) (IC(50)=147 nM) and alpha-3-beta-4 (CHRNA3-CHRNB4) (IC(50)166 nM), but no inhibition of alpha-3-beta-2 (CHRNA3-CHRNB2), alpha-4-beta-2 (CHRNA4-CHRNB2), alpha-4-beta-4 (CHRNA4-CHRNB4), alpha-6/alpha-3-beta-2-beta-3 (CHRNA6/CHRNA3-CHRNB2-CHRNB3), beta-3-alpha-6-beta-2-alpha-4-beta-2 (CHRNB3-CHRNA6-CHRNB2-CHRNA4-CHRNB2) nAChRs (PubMed:26330550). Post-translational modification of Pro-50 into hydroxyproline [P50O] induces a 9-fold decrease in inhibition of alpha-6/alpha-3-beta-2-beta-3 (CHRNA6/CHRNA3-CHRNB2-CHRNB3) and a 4-fold decrease in inhibition of alpha-6/alpha-3-beta-4 (CHRNA6/CHRNA3-CHRNB4). Does not inhibit alpha-4-beta-2 (CHRNA4-CHRNB2) nAChR (IC(50)=10.400 uM or >20 uM). Exists in two forms, due to cis-trans isomerization at 49-Pro-Pro-50. The synthetic peptide TP-2212-59, with the sequence GCCSHPBCFBZYC (B=Aminobutyric acid and Z=Norvaline), shows a high selectivity on alpha-3-beta-4/CHRNA3-CHRNB4 (IC(50)=2.3 nM on alpha-3-beta-4/CHRNA3-CHRNB4 and no inhibition on other receptors tested). Belongs to the conotoxin A superfamily.