High-resolution NMR studies of antibiotics in cell membranes

The alarming rise of antimicrobial resistance requires novel antibiotics with unexploited mechanisms. Ideal templates could be antibiotics that target Lipid II, known as the Achilles' heel of bacteria, at an irreplaceable pyrophosphate group. Such antibiotics, like nisin [1], plectasin [2], or teixobactin [3] would kill the most refractory pathogens without causing antimicrobial resistance. However, due to the challenge of studying small membraneembedded drug-receptor complexes in native conditions, the structural correlates of the pharmaceutically relevant binding modes are unknown. Here, using state-of-the-art solid-state NMR methods that enable atomic-resolution studies directly in native bacterial cell membranes, we report on the pharmaceutically relevant binding modes of Lipid II-peptide complexes.[4] We show on the example of nisin and plectasin, which are two of the preeminent Lipid II binding peptides, that previously published structures do not report on physiologically relevant drug binding modes, which we further validate with other biophysical data and extensive mutational studies in combination with activity tests. We do report comprehensive high-resolution data of the relevant physiological lipid II - peptide complexes, and we show how the intriguing complexity of bacterial membranes critically modulates the binding mode. Altogether, our high-resolution approach provides critical insights into the physiologically and pharmacologically relevant binding modes for a promising class of antibiotics.