Hefutoxin

Kappa- Hefutoxin 1 and 2 are toxins from the venom of the Asian forest black scorpion with a unique structure. It blocks the potassium channels Kv1.2 and Kv1.3 and slows the activation of Kv1.3.

Source
The kappa- Hefutoxin 1 and 2 (κ- Hefutoxin1/2) are the toxic components of the venom of the scorpion called Heterometrus fulvipes that belongs to the family scorpionidae. It is also known as the Asian Forest Black Scorpion and is distributed in South India, Indonesia and Malaysia.

Chemistry
The structure of the toxin is unique because it is made up of two parallel helices linked by two disulfide bridges without β- sheets. The κ- Hefutoxin1 consists of 22 residues and one amidated C terminus and is therefore the shortest scorpion toxin reported so far. The κ- Hefutoxin2 is build up of 23 residues with free C-terminus.

Target and mode of action
The toxin blocks the voltage-gated potassium channel Kv1.2 and not only blocks the Kv1.3 channels but also slows down their activation kinetics. The blocking effect is most effective when the K+ ions flow inward thus at a negative potential.