A novel toxin from the venom of the scorpion Tityus trivittatus, is the first member of a new α-KTX subfamily

The first example of a new sub-family of toxins (α-KTx20.1) from the scorpion Tityus trivittatus was purified, sequenced and characterized physiologically. It has 29 amino acid residues, three disulfide bridges assumed to adopt the cysteine-stabilized α/β scaffold with a pI value of 8.98. The sequence identities with all the other known α-KTx are less than 40%. Its effects were verified using seven different cloned K+ channels (vertebrate Kv1.1–1.5, Shaker IR and hERG) expressed in Xenopus leavis oocytes. The toxin-induced effects show large differences among the different K+ channels and a preference towards Kv1.3 (EC50 = 7.9 ± 1.4 nM).