Isolation of the first toxin from the scorpion Buthus occitanus israelis showing preference for Shaker potassium channels

We have purified BoiTx1, the first toxin from the venom of the Israeli scorpion, Buthus occitanus israelis, and studied its activity and genomic organization. BoiTx1 is a 37 amino acid-long peptide contained six conserved cysteines, and is classified as an α-KTx3.10 toxin. The pharmacological effects of BoiTx1 were studied on various cloned K+ channels expressed in Xenopus laevis oocytes. BoiTx1 inhibited currents through Drosophila Shaker channels with an IC50 value of 3.5 ± 0.5 nM, yet had much lesser effect on its mammalian orthologs. Thus, BoiTx1 is the first member of the α-KTx3 family that preferentially affects insect potassium channels.