Amino acid sequence determination and chemical synthesis of CllErg1 (gamma-KTx1.5), a K+ channel blocker peptide isolated from the scorpion Centruroides limpidus limpidus

Abstract

A novel toxin named CllErg1 (systematic nomenclature gamma-KTx1.5) was purified from the venom of the scorpion Centruroides limpidus limpidus and its amino acid sequence was determined. It has 42 amino-acid residues cross-linked by four disulfide bridges and blocks specifically a potassium channel of the family ether-a-go-go (ERG). The full peptide was chemically synthesized and properly folded, showing that it blocks the human ERG-channels (HERG) with identical affinity to that of the native peptide. Synthetic CllErg1 can be produced in quantities enough to compensate its low concentration in the natural venom. It paves the way to conduct studies aimed at the identification of the structural motifs of HERG critical for proper channel function. Additionally, another analogous peptide CllErg2 (systematic name gamma-KTx4.1) was purified and had its full amino acid sequence determined. It contained 43 amino acid residues, maintained closely packed by four disulfide bridges.