Serine protease inhibitor homolog that selectively blocks voltage-gated potassium channels homooligomer Kv1.1/KCNA1 (EC(50)=0.6 nM) and Kv1.1-containing heterooligomer. Expressed by the venom gland. LD(50) is 30 mg/kg by intravenous injection. Does not inhibit serine proteases and voltage-gated potassium channels Kv1.2/KCNA2 and Kv1.6/KCNA6. Belongs to the venom Kunitz-type family.