In-plane small angle neutron diffraction on the mechanism of anti microbial peptides action on bacterial cell membranes

Abstract

A new class of antimicrobials, in the form of small polypeptides, has been recently discovered in host defense systems throughout the animal kingdom [1–3]. For example, magainins (23-residue polypeptide). secreted by the skin of the African clawed frog. and cecropins (31–38 residues) isolated from the humoral immune systems of insects [1,3] kill bacteria by permeabilizing the cytoplasmic membrane, but do not lyse eukaryotic cells [3]. The present understanding is that all these antimicrobials exert their activity directly on the lipid bilayer of the bacterial cellular membrane, rather than interacting with specific proteins in a cell like the conventional antibiotics. Hence, it is believed that bacteria may not develop resistance to these drugs, but the intriguing question that has to be addressed is, if these antimicrobials act on membranes, how do they selectively attack bacteria without harming the host cells?