PURIFICATION AND CHARACTERIZATION OF A SCORPION DEFENSIN, A 4KDA ANTIBACTERIAL PEPTIDE PRESENTING STRUCTURAL SIMILARITIES WITH INSECT DEFENSINS AND SCORPION TOXINS

Insect defensins are a group of inducible small-sized antibacterial peptides with three intramolecular disulfide bridges. NMR studies have recently shown that they share striking structural similarities with scorpion toxins. We have investigated in a scorpion species, Leiurus quinquestriatus, the potential presence of antibacterial molecules and report the isolation and structural characterization of a novel insect defensin homologue, which we refer to as scorpion defensin. This peptide shows a remarkably high degree of sequence homology with a defensin recently characterized in a species belonging to the ancient insect order of the Odonata with which it defines a novel ancient subclass of defensins. The scorpion defensin has in common with the scorpion toxins a consensus sequence Cys-[.]-Cys-Xaa-Xaa-Xaa-Cys-[.]-Gly-Xaa-Cys-[.]-Cys-Xaa-Cys present in all scorpion toxins characterized so far. © 1993 Academic Press.