Interactions of antimicrobial and cell-penetrating peptides with lipid membranes

Antimicrobial, cytolytic, and cell-penetrating peptides, often called membrane-active peptides, belong to a variety of structural classes, including, alpha-helical, beta-sheet, unstructured, and cyclic polypeptides, among others. Those peptides were intensely studied in the 1990s and early 2000s with the hope of opening the door for urgently needed new antibiotics. For about 15 years we have studied the kinetics and thermodynamics of their interactions with lipid vesicles with the hope of understanding the mechanism of their function. In general, these peptides bind to lipid bilayers and somehow disrupt or perturb them, causing flux of ions and molecules across the membrane, and also, in some cases, translocating themselves across the membrane. In this talk, I will discuss our efforts to understand the mechanisms of these peptides and what we have learned regarding the effect of sequence on their ability to translocate across the membrane. I will conclude with the examination of a very different case, the cyclic peptide daptomycin, which is one of the few in clinical use. This peptide appears to behave very differently from all other membrane-active peptides that we have studied.