HgeTx1 (systematic name:α-KTx 6.14) is atoxin produced by the MexicanscorpionHoffmanihadrurus gertschi that is a reversible blocker of theShaker B K+-channel, a type ofvoltage-gated potassium channels.
The toxin HgeTx1 is produced by the Mexican scorpionHoffmanihadrurus gertschi, which belongs to the family ofCaraboctonidae.[1]HgeTx1 is the first toxin (Tx1) from this scorpion (Hge).[2] HgeTx1 belongs to theα-KTx potassium channel toxin category, and is placed in the sixth subfamily of all α-KTx toxins where HgeTx1 is the fourteenth member, which gives HgeTx1 its systematic name α-KTx 6.14.[3]
All α-KTx category toxins are peptides that contain between 20 and 40 amino acids and contain three or fourdisulfide bridges. HgeTx1 consists of 36 amino acids and has four disulfide bridges. These disulfide bridges exist betweenCys1–Cys5, Cys2–Cys6, Cys3–Cys7 and Cys4–Cys8. It has amolecular mass of 3950 atomic mass units.[2]
Electrophysiological experiments (whole cell configurationpatch clamping) have been performed to investigate the physiological effect of HgeTx1 onShaker B K+-channels in insect cell cultures. These recordings show that HgeTx1 reversibly blocks theShaker B K+-channel. This blockage follows aMichaelis-Menten saturation relationship with aKd of 52 nM.[2] However, there is no report of selectivity for or blockage of other subtypes of K+-channels.[2][4]
HgeTx1 has only been investigated for its effectiveness on theShaker B K+-channel, where the toxin seems to work as a plug that blocks the pore's ion conductance. This blockage follows the functional dyad model[5][6][7] that underlies most α-KTx toxins. In the functional dyad model, alysine residue interacts with a hydrophobicLeu,Tyr,Met orPhe residue, in order to recognize the K+-channel. On the extracellular side of the channel, the side-chain of the lysine residue will enter the pore and subsequently block the channel. In HgeTx1, it seems likely that the Lys24 residue will interact with the hydrophobic Met33 or Leu34 residue according to the functional dyad model, which allows it to block theShaker B K+-channel.[2]
Scorpions of the family Caraboctonidae, each of which produce a cocktail of different toxins, are not considered dangerous to humans.[2]
