Mu-conotoxin KIIIA-P1: mu-conotoxins block voltage-gated sodium channels (Nav). This toxin potently blocks Nav1.2/SCN2A (IC(50)5-124 nM), Nav1.4/SCN4A (IC(50)=20-90 nM), and Nav1.7/SCN9A (IC(50)=290-413 nM) (PubMed:17724025, PubMed:19221510, PubMed:21781281, PubMed:21709136,PubMed:21652775, PubMed:23146020, PubMed:25658507, PubMed:35167877). It moderately blocks Nav1.1/SCN1A, and mNav1.6/SCN8A (PubMed:17724025, PubMed:21781281, PubMed:21709136, PubMed:21652775, PubMed:23146020, PubMed:25658507, PubMed:35167877). It also shows a very low activity on Nav1.3/SCN3A (PubMed:17724025, PubMed:21781281). This toxin binds a microsite within the pore different from the tetrodotoxin binding site 1 (tested on Nav1.2) (PubMed:19221510). The block is partial, with a residual current that can be completely blocked by TTX (PubMed:19221510). The toxin probably docks at a more superficial site in the outer vestibule of the channel than does TTX (PubMed:19221510). On rNav1.2/SCN2A, it produces a block that is only partially reversible. The block of Nav1.7 is modified when beta-subunits are coexpressed with the alpha subunit (PubMed:23146020). Hence, blocks of channels containing beta-1 and beta-3 subunits are more potent (compared to channels without beta subunits), whereas blocks of channels containing beta-2 and beta-4 subunits are less potent (compared to channels without beta subunits) (PubMed:23146020). Mu-conotoxin KIIIA-P2: This toxin potently blocks Nav1.2/SCN2A (Kd=230 nM, IC(50)=1.37 uM) and Nav1.4/SCN4A (Kd=830 nM, IC(50)=2 uM). It also moderately blocks Nav1.7/SCN9A (Kd=1.57 uM, IC(50)=5.4 uM) (PubMed:35167877, PubMed:23167564). In addition, this toxin may also inhibit other sodium channels, as does Mu-conotoxin KIIIA-P1 (PubMed:23167564). Mu-conotoxin KIIIA-N: This toxin moderately blocks Nav1.2/SCN2A (IC(50)=875 nM), Nav1.4/SCN4A (IC(50)=472 nM), and Nav1.7/SCN9A (IC(50)=887 nM) (PubMed:35167877). Mu-conotoxin KIIIB-P1: This toxin potently blocks Nav1.2/SCN2A (Kd=470 nM). In addition, this toxin may also inhibit other sodium channels, as does Mu-conotoxin KIIIA-P1. Mu-conotoxin KIIIB-P2: This toxin potently blocks Nav1.2/SCN2A (Kd=26 nM). In addition, this toxin may also inhibit other sodium channels, as does Mu-conotoxin KIIIA-P1. Monomer. 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. Toxins with three different disulfide connectivities have been synthesized (PubMed:35167877, PubMed:23167564). The conotoxin mu-KIIIA-P1 shows the connectivity C1-C5, C2-C4, and C3-C6, whereas mu-KIIIA-P2 shows the connectivity C1-C6, C2-C4, and C3-C5 (PubMed:23167564). The conotoxin mu-KIIIA-N has the 'native' fold of the mu-conotoxin family (C1-C4, C2-C5, and C3-C6) (PubMed:35167877). Mu-KIIIA-P1 and mu-KIIIA-P2 are obtained by both thermodynamic oxidative folding and regioselective synthesis (PubMed:35167877, PubMed:23167564). Mu-KIIIA-P1 is the major oxidative folding product (PubMed:23167564). Mu-KIIIA-N is only obtained by regioselective synthesis (PubMed:35167877). Has no effect on hNav1.5/SCN5A (PubMed:17724025, PubMed:21781281, PubMed:25658507). Has no effect on hNav1.8/SCN10A (PubMed:21781281). Belongs to the conotoxin M superfamily.