Mu-conotoxins block voltage-gated sodium channels (Nav). Blocks reversibly sodium channels in molluskan neurons, but has no effect on sodium currents in bovine chromaffin cells or in rat brain synaptosomes (By similarity). Induces paralysis in mollusks (C.retripictus) (PubMed:28831846). Expressed by the venom duct. The cysteine framework is IV (CC-C-C-C-C). Contains 3 disulfide bonds. They are not added, since framework IV presents two different connectivities (I-V, II-III, IV-VI and I-III, II-V, IV-VI). Monoisotopic mass. PD(50) is 0.2-0.4 nmol/g when injected into the foot of the freshwater snail C.retropictus. Belongs to the conotoxin M superfamily.