Effects of temporins on molecular dynamics and membrane permeabilization in lipid vesicles

Temporins are a novel family of small (10-13 residues) cationic antimicrobi al peptides recently isolated from the skin of the European red frog Rana t emporaria. Although recently acquired evidence shows that temporins have th e potential to kill bacteria by permeabilizing the cytoplasmic membrane, th e molecular mechanisms of membrane selectivity and permeabilization are lar gely unknown. In this study, it was found that temporins cause the release of fluorescent markers entrapped in phosphatidylcholine liposomes in a mann er that depends significantly on the size of the solute. Temporins were cor respondence to: also shown to lack a detergent-like effect on lipid vesicle s, indicating that marker leakage caused by these peptides is not due to to tal membrane disruption but to perturbation of bilayer organization on a lo cal scale. Binding of temporins to liposomes did lead to a small increase i n lipid hydrocarbon chain mobility, as revealed by EPR spectroscopy of nitr oxide-labeled fatty acids incorporated in the bilayer. Reference experiment s were conducted using the bee venom peptide melittin, whose properties and behavior in natural and it model membrane systems are well known. Our find ings for temporins are discussed in relation to the models proposed to date to account for the action of antimicrobial peptides on membranes.