The antibiotic and anticancer active aurein peptides from the Australian Bell Frogs Litoria aurea and Litoria raniformis - The solution structure of aurein 1.2

Seventeen aurein peptides are present in the secretion from the granular do rsal glands of the Green and Golden Bell Frog Litoria aurea, and 16 from th e corresponding secretion of the related Southern Bell Frog L. raniformis. Ten of these peptides are common to both species. Thirteen of the aurein pe ptides show wide-spectrum antibiotic and anticancer activity. These peptide s are named in three groups (aureins 1-3) according to their sequences. Amo ngst the more active peptides are aurein 1.2 (GLFDIIKKIAESF-NH2), aurein 2. 2 (GLFDIVKKVVGALGSL-NH2) and aurein 3.1 (GLFDIVKKIAGHIAGSI-NH2). Both L. au rea and L. raniformis have endoproteases that deactivate the major membrane -active aurein peptides by removing residues from both the N- and C-termini of the peptides. The most abundant degradation products have two residues missing from the N-terminal end of the peptide. The solution structure of t he basic peptide, aurein 1.2, has been determined by NMR spectroscopy to be an amphipathic alpha-helix with well-defined hydrophilic and hydrophobic r egions. Certain of the aurein peptides (e.g. aureins 1.2 and 3.1) show anti cancer activity in the NCI test regime, with LC50 values in the 10(-5)-10(- 4) m range. The aurein 1 peptides have only 13 amino-acid residues: these a re the smallest antibiotic and anticancer active peptides yet reported from an anuran. The longer aurein 4 and 5 peptides, e.g. aurein 4.1 (GLIQTIKEKL KELAGGLVTGIQS-OH) and aurein 5.1 (GLLDIVTGLLGNLIVDVLKPKTPAS-OH) show neithe r antibacterial nor anticancer activity.