Interaction between antimicrobial peptides (AMPs) and their primary target, the biomembranes

Antimicrobial peptides (AMPs) are produced by almost all living organisms as a component of their immune system representing the first line weapons against infective agents. During the past two decades these key factors of the innate immunity have been isolated from many different organisms including mammals, insects, plants; bacteria and amphibians. Although AMPs are an heterogeneous group of peptides they share three common properties, in fact they are: i) generally short (8-50 amino acids), ii) amphipathic and iii) carrying a net positive charge. Even if intracellular targets of AMPs such as DNA, RNA and/or proteins have been described, the primary target of these molecules appears to be the cell membrane. It has been demonstrated that AMPs interact directly with the microbial cell membranes inducing an increase in permeability and then causing cell lysis. The interaction of these peptides with membrane components, mainly phospholipids, might be the trigger of pore formation, thinning of the membrane or bilayer destabilization. In this paper we discuss about the proposed mechanisms of AMPs/biomembrane interactions as well as on the use of synthetic membranes (liposomes and lipid monolayers) to elucidate these aspects.