Magic bullets to fight resistance: Uncovering how peptide-antibiotics break down the bacterial cell envelope

Abstract

The rapid rise of resistant bacteria urgently calls for novel antibiotics that are robust to resistance development. Ideal templates could be peptide-antibiotics that destroy the bacterial cell wall by binding to its membrane-anchored precursor lipid II at irreplaceable phosphate groups. Indeed, these drugs can kill the most refractory bacteria without detectable resistance. However, due to the challenge of studying antibiotic-receptor complexes in membranes, structural information on these highly promising drugs is extremely small and physiological binding modes could never be visualized. This lack of knowledge critically limits the development and application of lipid II attacking drugs. Here we present extensive high-resolution data of lipid II peptide-antibiotics in physiological conditions. These studies were enabled by the use of cutting-edge 1H-detected solid-state NMR experiments acquired at 950 MHz and very fast sample spinning. We first show comphrehensive structural data of the nisin-lipid II pore, acquired in liposomes and directly in native bacterial cell membranes. Nisin is the most prominent lipid II binding peptide and kills bacteria by a unique mechanism called targeted pore formation. Despite of extensive research, structural models of the nisinlipid II pore have been lacking hithero. Furthermore, we present progress towards a solid-state NMR structure of the plectasinlipid II complex. Plectasin is a defensin with strong potential to kill multi-resistant superbugs such as MRSA. Our data, acquired in native-like membranes, reveal the drug-binding interface and show that plectasin exhibits several binding modes in physiological conditions. Moreover, we analyze the dynamics of bound and unbound plectasin, which is of great value to optimize antibiotic binding. We expect our data to critically improve our understanding of lipid II binding peptides, which is an important step towards the medical use of these powerful antibiotics.