HgeTx1, the first K+-channel specific toxin characterized from the venom of the scorpion Hadrurus gertschi Soleglad

A novel toxin was identified, purified and characterized from the venom of the Mexican scorpion Hadrurus gertschi (abbreviated HgeTx1). It has a molecular mass of 3950 atomic mass units (a.m.u.) and contains 36 amino acids with four disulfide bridges established between Cys1–Cys5, Cys2–Cys6, Cys3–Cys7 and Cys4–Cys8. It blocks reversibly the Shaker B K+-channels with a Kd of 52 nM. HgeTx1 shares 60%, 45% and 40% sequence identity, respectively, with Heterometrus spinnifer toxin1 (HsTX1), Scorpio maurus K+-toxin (maurotoxin) and Pandinus imperator toxin1 (Pi1), all four-disulfide bridged toxins. It is 57–58% identical with the other scorpion K+-channel toxins that contain only three disulfide bridges. Sequence comparison, chain length and number of disulfide bridges analysis classify HgeTx1 into subfamily 6 of the α-KTx scorpion toxins (systematic name: α-KTx 6.14).