Selective inhibitor of voltage-gated potassium channel Kv10.1/KCNH1/EAG1 (IC(50)=637 nM). It acts by shifting the voltage dependence of channel activation in a depolarising direction. It shows a 100% inhibition at saturating concentrations, shows fast on-rates and is reversible. It also slightly affects channel inactivation, when the membrane is highly depolarised (>+80 mV). Expressed by the venom gland. The presence of a 'disulfide through disulfide knot' structurally defines this protein as a knottin. Monoisotopic mass. Could be used as informative lead for the development of novel antiepileptic drugs, as well as pharmacological tool for probing Kv10.1/KCNH1/EAG1 function. Weakly inhibits Nav1.2/SCN2A (IC(50)=1449 nM), Nav1.7/SCN9A (IC(50)=1528 nM), Nav1.5/SCN5A (IC(50)=7316), and Kv11.1/KCNH2/ERG1 (IC(50)=8511 nM). Belongs to the neurotoxin 10 (Hwtx-1) family.