Disulfide bridges and blockage of Shaker BK+-channels by another butantoxin peptide purified from the Argentinean scorpion Tityus trivittatus

A peptide was isolated from the venom of the scorpion Tityus trivittatus. It is an isoform of the toxin TsTX-IV earlier described [Toxicon 37 (1999) 651] and identical to butantoxin [Arch. Biochem. Biophys. 379 (2000) 18], both isolated from the Brazilian scorpion Tityus serrulatus. This newly characterized peptide contains 40 amino acid residues with a molecular mass of [M + H+] 4507.0, cross-linked by four disulfide bridges, made between the cysteine pairs: Cys2-Cys5, Cys10-Cys31, Cys16-Cys36 and Cys20-Cys38. It blocks in a completely reversible manner the Shaker B K+-channels, with a K-d around 660 nM. It belongs to the sub-family 12 and it is now being classified as alpha-KTx 12.2. (C) 2002 Elsevier Science Ltd. All rights reserved.