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. Induces paralysis in bivalve mollusks (Mytilus). No effect are observed on fish (Gambusia) and fly larvae (Sarcophaga). Is approximately 6 times more potent than PnIVA in blockade of the sodium current in Lymnaea neurons. Expressed by the venom duct. The cysteine framework is IV (CC-C-C-C-C). Contains 3 disulfide bonds (By similarity). They are not added, since framework IV presents two different connectivities (I-V, II-III, IV-VI and I-III, II-V, IV-VI). Belongs to the conotoxin M superfamily.