Potent and specific blocker of Kv4.2/KCND2 (IC(50)=5 nM) and Kv4.3/KCND3 (IC(50)=28 nM) potassium channels (PubMed:10051143). Acts by altering the gating properties of these channels (PubMed:10051143). Also shows moderate inhibition on human voltage-gated sodium channel Nav1.7/SCN9A activation (IC(50)=423 nM) (PubMed:25026046). Expressed by the venom gland. The presence of a 'disulfide through disulfide knot' structurally defines this protein as a knottin. This toxin does not inhibit Kv1/KCNA, Kv2/KCNB, Kv3/KCNC, and Kv11/KCNH channels (PubMed:10051143). It weakly blocks the neuronal TTX-sensitive sodium currents of neuroblastoma cells (13% inhibition at 100 nM) (PubMed:10051143). Does not inhibit sodium channel Nav1.2/SCN2A (PubMed:25026046). Belongs to the neurotoxin 30 (phrixotoxin) family.