Assembly and Stability of Nisin−Lipid II Pores

Abstract

The peptide antibiotic nisin was the first reported example of an antibiotic that kills bacteria via targeted pore formation. The specific target of nisin is Lipid II, an essential intermediate in the bacterial cell-wall synthesis. High-affinity binding of the antibiotic to Lipid II is followed by rapid permeabilization of the membrane. Here, we investigated the assembly and stability of nisin-Lipid II pore complexes by means of pyrene fluorescence and circular dichroism. We demonstrated that nisin uses all available Lipid II molecules in the membrane to form pore complexes. The pore complexes have a uniform structure and consist of 8 nisin and 4 Lipid II molecules. Moreover, the pores displayed a remarkable stability, because they were able to resist the solubilization of the membrane environment by mild detergents. Similar experiments with [N20P/M21P]nisin showed that the hinge region is essential for the assembly into stable pore complexes. The new insights were used to propose a refined model for nisin pore formation.

The action mechanism of daptomycin

“…A precedent for such a dual mechanism of action is provided by the lantibiotic nisin. 87,119 In addition to the mechanism of action, much work remains to be done regarding daptomycin's structure-activity relationships. A larger and more diverse set of sequence variants is needed, which should be examined for antimicrobial activity, but also using biophysical and biochemical methods that illuminate specific steps in the action mode of daptomycin.…”

A crystal structure of a dimer of the antibiotic ramoplanin illustrates membrane positioning and a potential Lipid II docking interface

“…Mersacidin forms a tightly associated 1:1 complex with Lipid II, and nisin sequesters Lipid II via encapsulating the pyrophosphate of Lipid II within a hydrogen bond network formed by nisin backbone amides (36,37). The nisin-Lipid II complex organizes into a supramolecular pore-like assembly, engendering a breach in membrane integrity and leading to cell death by osmotic lysis (38)(39)(40). Common to both mersacidin and nisin are structural changes within the antibiotic that are triggered by the encounter with the membrane environment.…”

“…Once two dimers come together in such a manner, additional Lipid II molecules could then bind at the uncomplexed ends of these dimers, recruit additional dimers, and so on, ultimately forming a polymeric structure with a ramoplanin-Lipid II stoichiometry of 2:1. We do not yet know if ramoplanin and Lipid II organize into supramolecular assemblies within the membrane, as is the case for the pore-like complex formed by the nisin-Lipid II complex (40,42). However, it is intriguing to speculate that the ligand-induced polymerization of ramoplanin that is observed with soluble Lipid II analogues may reflect an intrinsic property of the antibiotic, and that formation of such high order assemblies promotes the antibacterial activity.…”

Efficient production of active form of vitamin D3 by microbial conversion

“…Nisin is an antibacterial peptide composed of 34 amino acids derived from Lactococcus lactis, and is approved as food additive. The action mechanism of nisin has been studied thoroughly, and it shows antibacterial activity by creating pores with diameters of about 2-2.5 nm in the membrane of the gram-positive bacteria, and the intracellular low molecular substances leak outside of the cell through the pores [12] . Although excessive addition of nisin will cause bacteriolysis, the R. erythropolis cell is characterized by bacteriolysis resistance compared to other bacteria.…”