The role of lipid II in membrane binding of and pore formation by nisin analyzed by two combined biosensor techniques

Abstract

Nisin, a peptide antibiotic, efficiently kills bacteria through a unique mechanism which includes inhibition of cell wall biosynthesis and pore formation in cytoplasmic membranes. Both mechanisms are based on interaction with the cell wall precursor lipid II which is simultaneously used as target and pore constituent. We combined two biosensor techniques to investigate the nisin activity with respect to membrane binding and pore formation in real time. Quartz crystal microbalance (QCM) allows the detection of nisin binding kinetics. The presence of 0.1 mol% lipid II strongly increased nisin binding affinity to DOPC (k(D) 2.68 x 10(-7) M vs. 1.03 x 10(-6) M) by a higher association rate. Differences were less pronounced while using negatively charged DOPG membranes. However, lipid II does not influence the absolute amount of bound nisin. Cyclic voltammetry (CV) data confirmed that in presence of 0.1 mol% lipid II, nanomolar nisin concentrations were sufficient to form pores, while micromolar concentrations were necessary in absence of lipid II. Both techniques suggested unspecific destruction of pure DOPG membranes by micromolar nisin concentrations which were prevented by lipid II. This model membrane stabilization by lipid II was confirmed by atomic force microscopy. Combined CV and QCM are valuable to interpret the role of lipid II in nisin activity.

Multiple Peptide Resistance Factor (MprF)-mediated Resistance of Staphylococcus aureus against Antimicrobial Peptides Coincides with a Modulated Peptide Interaction with Artificial Membranes Comprising Lysyl-Phosphatidylglycerol

“…It has been shown very recently that carotenoid content of the cytoplasmic membrane affects susceptibility of S. aureus to certain AMPs probably by reduction of membrane fluidity (44). Lipid II, a precursor for cell wall synthesis, is used as a receptor for membrane binding and subsequent permeabilization by certain antimicrobial peptides termed lantibiotics (8,9). It is tempting to speculate that the balance between lipid II and lysyl-PG fine-tunes the efficacy of those peptides against S. aureus.…”

Structural Variations of the Cell Wall Precursor Lipid II and Their Influence on Binding and Activity of the Lipoglycopeptide Antibiotic Oritavancin

“…To further validate the data obtained from the in vitro assays, the binding parameters of oritavancin and vancomycin to selected lipid II variants (lipid II, lipid II-Gly 5 , amidated lipid II, amidated lipid II-Gly 5 , lipid II-D-Lac, and amidated lipid II-D-Lac) were determined using a quartz crystal microbalance (QCM) technique (48)(49)(50).…”

“…After equilibration of the quartz crystals under flow conditions until they reached a constant frequency, 1 M peptide solution was added. The frequency curves allow the calculation of the kinetic binding constants as described previously (49,50).…”

Analysis of membrane interactions of antibiotic peptides using ITC and biosensor measurements

“…The modification of the quartz crystals has already been described [24,25]. A DOPC or DOPG ± 0.1 mol% lipid II layer was transformed by Langmuir-Blodgett technique onto a 1-hexadecanethiol covered quartz crystal.…”