Mu-conotoxins block voltage-gated sodium channels (Nav). Expressed by the venom duct. The cysteine framework is III (CC-C-C-CC). Classified in the M-2 branch, since 2 residues stand between the fourth and the fifth cysteine residues. Contains 3 disulfide bonds. with hydroxyPro-67. Belongs to the conotoxin M superfamily.