Potent and specific blocker of Kv4.2/KCND2 (IC(50)=34 nM) and Kv4.3/KCND3 (IC(50)=71 nM) potassium channels (PubMed:10051143). Acts by altering the gating properties of these channels (PubMed:10051143). Expressed by the venom gland. The presence of a 'disulfide through disulfide knot' structurally defines this protein as a knottin. The primary structure of this mature peptide is identical to that of kappa-theraphotoxin-Gr2a (GsMTx-2) from Grammostola rosea (AC P60273). Is the most abundant peptide in the venom. 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 (14% inhibition at 500 nM) (PubMed:10051143). Belongs to the neurotoxin 30 (phrixotoxin) family.