Arthropod defensins illuminate the divergence of scorpion neurotoxins

Defensins are phylogenetically ancient antibacterial polypeptides found in plants and animals. Isolation of the cDNA and genomic sequences encoding the scorpion ( Leiurus quinquestriatus hebraeus ) defensin revealed similarity to scorpion neurotoxins in gene organization (two exons and a phase I intron) and intron characteristics (conserved acceptor, donor and putative branch sites). This commonality, alongside a similar core structure, protein sequence and bioactivity suggest that arthropod defensins and scorpion neurotoxins share a common ancestor. Interestingly, phylogenetic analysis of defensins and scorpion neurotoxins illuminates for the first time a putative evolutionary trajectory for scorpion sodium and potassium channel neurotoxins. Copyright © 2004 European Peptide Society and John Wiley & Sons, Ltd.