Lt1.3-II (C1-C3; C2-C4): Alpha-conotoxins act on postsynaptic membranes, they bind to the nicotinic acetylcholine receptors (nAChR) and thus inhibit them. This toxin potently and selectively inhibits alpha-3-beta-2/CHRNA3-CHRNB2 (IC(50)=44.8 nM) nAChRs. Lt1.3-I (C1-C4; C2-C3): This isomer inhibits GABABRec-coupled Cav2.2/CACNA1B but has no activity on nAChRs. Expressed by the venom duct. The cysteine framework is I (CC-C-C). Alpha4/7 pattern. Lt1.3-II (C1-C3; C2-C4): this synthetic toxin shows no or very weak inhibition on alpha-2-beta-2/CHRNA2-CHRNB2, alpha-2-beta-4/CHRNA2-CHRNB4, alpha-3-beta-4/CHRNA3-CHRNB4, alpha-4-beta-2/CHRNA4-CHRNB2, alpha-4-beta-4/CHRNA4-CHRNB4, alpha-7/CHRNA7, alpha-9-alpha-10/CHRNA9-CHRNA10, and GABAB-Rec-coupled Cav2.2/CACNA1B. Belongs to the conotoxin A superfamily. This toxin has been called Lt1.3 b, since the name Lt1.3 is already attributed to AC Q2I2R6.