Kappa- Hefutoxin 1 and 2 are
toxin
A toxin is a naturally occurring organic poison produced by metabolic activities of living cells or organisms. Toxins occur especially as a protein or conjugated protein. The term toxin was first used by organic chemist Ludwig Brieger (1849– ...
s from the
venom
Venom or zootoxin is a type of toxin produced by an animal that is actively delivered through a wound by means of a bite, sting, or similar action. The toxin is delivered through a specially evolved ''venom apparatus'', such as fangs or a sti ...
of the Asian forest black
scorpion
Scorpions are predatory arachnids of the order Scorpiones. They have eight legs, and are easily recognized by a pair of grasping pincers and a narrow, segmented tail, often carried in a characteristic forward curve over the back and always end ...
''
Heterometrus
''Heterometrus'', whose members are also known by the collective vernacular name giant forest scorpions, is a genus of scorpions belonging to the family Scorpionidae. It is distributed widely across tropical and subtropical southeastern Asia, in ...
fulvipes'' with a unique structure. It blocks the
potassium channels Kv1.2 and Kv1.3 and slows the activation of Kv1.3.
The kappa- Hefutoxin 1 and 2 (κ- hefutoxin1/2) are toxic components in the venom of ''Heterometrus fulvipes'' that belongs to the family
scorpionidae
The Scorpionidae (burrowing scorpions or pale-legged scorpions) make up the Taxonomic rank, superfamily Scorpionoidea. The family was established by Pierre André Latreille, 1802.
Genera
Scorpionidae contains the following genera:
* ''Aops'' V ...
. 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 anti-parallel
helices
A helix () is a shape like a corkscrew or spiral staircase. It is a type of smooth space curve with tangent lines at a constant angle to a fixed axis. Helices are important in biology, as the DNA molecule is formed as two intertwined helices, ...
linked by two
disulfide bridges without
β- sheets. The κ- hefutoxin1 consists of 22 residues and with an amidated C terminus and is the shortest scorpion toxin reported so far. The κ- hefutoxin2 is built 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.<
References
{{Toxins
Neurotoxins
Ion channel toxins
Scorpion toxins