Direct visualization of the lytic action of antibiotic peptides.

AMBROGGIO E.E.,; SEPAROVIC F.,; BOWIE J.H.,; FIDELIO G.D.,; BAGATOLLI L.A,

CELL PRESS

Año: 2005 vol. 89 p. 1874 - 1874

p style="margin: 0cm 0cm 0pt;" class="MsoNormal">Membrane lysis caused by antibiotic peptides is often rationalized by means of two different models: the so-called carpet model and the pore-forming model. We report here on the lytic activity of antibiotic peptides from Australian tree frogs, maculatin 1.1, citropin 1.1, and aurein 1.2, on POPC or POPC/POPG model membranes. Leakage experiments using fluorescence spectroscopy indicated that the peptide/lipid mol ratio necessary to induce 50% of probe leakage was smaller for maculatin compared with aurein or citropin, regardless of lipid membrane composition. To gain further insight into the lytic mechanism of these peptides we performed single vesicle experiments using confocal fluorescence microscopy. In these experiments, the time course of leakage for different molecular weight (water soluble) fluorescent markers incorporated inside of single giant unilamellar vesicles is observed after peptide exposure. We conclude t