Interaction of type A lantibiotics with undecaprenol-bound cell envelope precursors.

Lantibiotics are a unique group within the antimicrobial peptides characterized by the presence of thioether amino acids (lanthionine and methyllanthionine). These peptides are produced by and primarily act on Gram-positive bacteria exerting multiple activities at the cytoplasmic membrane of susceptible strains. Previously, the cell wall precursor lipid II was identified as the molecular target for the prototype lantibiotic nisin. Binding and sequestration of lipid II blocks the incorporation of the central cell wall precursor into the growing peptidoglycan network, thereby inhibiting the formation of a functional cell wall. Additionally, nisin combines this activity with a unique target-mediated pore formation, using lipid II as a docking molecule. The interaction with the pyrophosphate moiety of lipid II is crucial for nisin binding. We show that, besides binding to lipid II, nisin interacts with the lipid intermediates lipid III (undecaprenol-pyrophosphate-N-acetyl-glucosamine) and lipid IV (undecaprenol-pyrophosphate-N-acetyl-glucosamine-N-acetyl-mannosamine) of the wall teichoic acid (WTA) biosynthesis pathway. Binding of nisin to the precursors was observed at a stoichiometry of 2:1. The specific interaction with WTA precursors further promoted target-mediated pore formation in artificial lipid bilayers. Specific interactions with lipid III and lipid IV could also be demonstrated for related type A lantibiotics, for example, gallidermin, containing the conserved lipid-II-binding motif.