Comparison of reversible membrane destabilisation induced by antimicrobial peptides derived from Australian frogs

Abstract

The membrane destabilising properties of the antimicrobial peptides (AMP) aurein 1.2, citropin 1.1, maculatin 1.1 and caerin 1.1, have been studied by dual polarisation interferometry (DPI). The overall process of peptide induced membrane destabilisation was examined by the changes in bilayer order as a function of membrane-bound peptide mass per unit area and revealed three different modes of action. Aurein 1.2 was the only peptide that significantly destabilised the neutral membrane (DMPC), while all four peptides induced destabilisation of the negatively charged membrane (DMPC/DMPG). On DMPC, citropin 1.1, maculatin 1.1 and caerin 1.1 bound irreversibly at low concentrations but caused a reversible drop in the bilayer order. In contrast to DMPC/DMPG, these three peptides caused a mass drop at the higher concentrations, which may correspond to insertion and bilayer expansion. The critical level of bound peptide necessary to induce membrane destabilisation (peptide:lipid ratio) was determined and correlated with peptide structure. As the most lytic peptide, aurein 1.2 adsorbed strongly prior to dissolution of the bilayer. In contrast, the binding of citropin 1.1, maculatin 1.1 and caerin 1.1 needed to reach a critical level prior to insertion into the membrane and incremental expansion and disruption. Our results demonstrate that sequential events can be monitored in real-time under fluidic conditions to elucidate the complex molecular mechanism of AMP action. In particular, the analysis of birefringence in real time allows the description of a detailed mechanistic model of the impact of peptides on the membrane bilayer order. This article is part of a Special Issue entitled: Interfacially Active Peptides and Proteins. Guest Editors: William C. Wimley and Kalina Hristova.

Multimerization of a Proline-Rich Antimicrobial Peptide, Chex-Arg20, Alters Its Mechanism of Interaction with the Escherichia coli Membrane

“…Antimicrobial peptides that are known to induce membrane disruption act on the inner/cytoplasmic membrane, which is known to contain disulfide bond-reducing proteins and have a redox potential that favors disulfide bond disruption (Eser et al, 2009;Kadokura et al, 2003). Furthermore, the bacterial membrane is highly fluid and dynamic, and the lytic action of some AMPs has been shown to be reversible (Gee et al, 2013;Hall et al, 2014;Lee et al, 2014). Thus the decline in activity from that measured by flow cytometry (MPC) and that measured by the growth assays (MIC and MBC) is probably due to two factors: the fluid/dynamic nature and disulfide bond-reducing environment of the inner membrane.…”

Antimicrobial Peptide Structures: From Model Membranes to Live Cells

“…We have used a range of techniques to determine the mode of action, such as solid‐state NMR, circular dichroism (CD), calorimetry, monolayer studies, surface plasmon resonance, dual polarization interferometry, quartz crystal microbalance, neutron reflectometry and molecular dynamics (MD) simulations. In general, the longer peptides form transmembrane or toroidal pores while the shorter peptides act by a “carpet” or surface mechanism . However, the mechanism (Figure ) depends on the type of lipid and peptide concentration.…”

Helix 8 of the angiotensin- II type 1A receptor interacts with phosphatidylinositol phosphates and modulates membrane insertion

“…The changes in membrane order as a result of AT 1 R-H8 binding were quantitatively examined through the measurement of the changes in optical birefringence (∆ n f ) of the bilayer simultaneously with the membrane-bound peptide mass ( m p ) in real time as previously described2627282930. In particular, the effect of lipid composition on the binding of AT 1 R-H8 to the membrane mimics (DMPC, DMPC/DMPS (80:20), DMPC/DMPS/PI(4)P(76:20:4) and DMPC/DMPS/PI(4,5)P 2 (76:20:4)) was analysed by DPI.…”

“…In this study we used DPI to analyze the binding of the binding of AT 1 R-H8 to various bilayer types, some of which include PIPs. DPI is an optical biosensor technology which not only provides information on binding interactions but also allows the measurement of changes in membrane structure in terms of thickness and bilayer order2627282932. We have also previously demonstrated that changes in membrane structure by antimicrobial peptides observed with DPI correlate well with solid state NMR33, and also neutron reflectometry34.…”