Inhibitor of voltage-gated potassium channels. Inhibits Kv2.1/KCNB1 channels, by shifting activation of the channel to more depolarized voltages. The toxin binding sites may be situated on the S3-S4 extracellular linker of the channel. One, two, three or four toxin molecules may bind the Kv2.1/KCNB1 channel. May need to partition into the membrane in order to bind to the channel. Antibacterial activity is not observed. 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. 09 (HaTx) subfamily.