This model contains Kunitz-type serine protease inhibitor huwentoxin-XI, including U15-theraphotoxin-Hs1g (also called U15-TRTX-Hs1g or Huwentoxin HW11c39), and kappaPI-theraphotoxin-Hs1a (also called KappaPI-TRTX-Hs1a or Huwentoxin-HW11g8). Huwentoxin-XI is a bifunctional toxin that inhibits both serine proteases (trypsin) and voltage-gated potassium channels (Kv) via surfaces displayed on opposite faces of the toxin. The structures of these domains are similar to those of Kunitz-type proteinase inhibitors such as BPTI (bovine pancreatic trypsin inhibitor), showing an alpha/beta fold with irregular secondary structure stabilized by three disulfide bonds.