Serine protease inhibitor homolog that blocks voltage-gated potassium channels (Kv1.1/KCNA1, Kv1.2/KCNA2, and Kv1.6/KCNA6) (IC(50)=0.4-150 nM) and facilitates neurotransmitter release. Expressed by the venom gland. LD(50) is 23 mg/kg by intravenous injection. Does not inhibit serine proteases and voltage-gated potassium channels Kvl.3/KCNA3, Kv1.4/KCNA4, Kv1.5/KCNA5, Kv3.1/KCNC1, Kv3.4/KCNC4, and Kv4.1/KCND1. Belongs to the venom Kunitz-type family.