Mu-conotoxins block voltage-gated sodium channels (Nav). This synthetic toxin blocks slightly but irreversibly tetrodotoxin-resistant VGSCs. Expressed by the venom duct. The cysteine framework is III (CC-C-C-CC). Classified in the M-5 branch, since 5 residues stand between the fourth and the fifth cysteine residues. CnIIIB. [Gln1]-CnIIIB. Found in injectable (milked) (IV) venom. Belongs to the conotoxin M superfamily.