This toxin acts as a voltage-dependent gating-modifier (PubMed:25240294). It inhibits the sodium conductance (IC(50)=124 nM) and slows the fast inactivation (EC(50)=1180 nM) of Nav1.5/SCN5A (PubMed:17176080, PubMed:25240294). It significantly shifts the activation to more depolarized voltages and decreases the deactivation of Nav1.5 currents upon extreme depolarization, but only slightly affects voltage-dependence of steady-state inactivation (PubMed:17176080, PubMed:25240294). In addition, this toxin causes an approximately five-fold decrease in the rate of recovery from inactivation and an approximately 1.9-fold reduction in the closed-state inactivation rate (PubMed:25240294). This toxin integrates the functions of site 3 toxins (alpha-scorpion toxins) with site 4 toxins (beta-scorpion and spider toxins) by targeting multiple sites on Nav1.5 (PubMed:25240294). Also shows inhibition of voltage-gated potassium channels (5 uM completely inhibits Kv2.1/KCNB1, whereas 5 uM moderately inhibits Kv4.2/KCND2 Kv4.1/KCND1 channels) (PubMed:17176080). Expressed by the venom gland. The presence of a 'disulfide through disulfide knot' structurally defines this protein as a knottin. This toxin does not show effect on Kv1.1/KCNA1, Kv1.2/KCNA2, Kv1.3/KCNA3, Kv1.4/KCNA4, Kv3.1/KCNC1 (all expressed in oocytes), voltage-gated sodium channels (Nav1/SCN) (from DRG neurons), and in a range of voltage-gated calcium channels (expressed in rat DRG neurons) (PubMed:17176080). Does not show significant toxic symptoms when injected into mice and into cockroaches (PubMed:17176080). Belongs to the neurotoxin 10 (Hwtx-1) family. 28 (Jztx-11) subfamily.