Moderately inhibits voltage-gated sodium channels and weakly inhibits voltage-gated potassium channel (PubMed:17150181, PubMed:17618665, PubMed:23246579, PubMed:26721415). Inhibits the inactivation of rat Nav1.2/SCN2A (IC(50)=870 nM), rat Nav1.3/SCN3A (IC(50)=845 nM), rat Nav1.4/SCN4A (IC(50)=339 nM), human Nav1.5/SCN5A (IC(50)=335 nM) and human Nav1.7/SCN9A sodium channels (IC(50)=348 nM) (PubMed:26721415). The toxin delays the inactivation of sodium channels without affecting the activation and steady-state inactivation kinetics in the physiological range of voltages (PubMed:26721415). Site-directed mutagenesis of the sodium channel indicates that the toxin interacts with site 3 located at the extracellular S3-S4 linker of domain IV (PubMed:26721415). On potassium channels, it inhibits activation of channels with an IC(50) of 8.05 uM through a voltage sensor-trapping mechanism (PubMed:23246579). It increases muscle contraction in several assays (mouse phrenic nerve-diaphragm, toad heart, rat vas deferens) and is suggested to act both presynaptically and postsynaptically (PubMed:17618665). Expressed by the venom gland. The presence of a 'disulfide through disulfide knot' structurally defines this protein as a knottin. Belongs to the neurotoxin 10 (Hwtx-1) family. 33 (Jztx-1) subfamily.