Interactions of a lytic peptide with supported lipid bilayers investigated by time-resolved evanescent wave-induced fluorescence spectroscopy

Abstract

We report investigations, using time-resolved and polarised evanescent wave-induced fluorescence methods, into the location, orientation and mobility of a fluorescently labelled form of the antimicrobial peptide, melittin, when it interacts with vesicles and supported lipid bilayers (SLBs). This melittin analogue, termed MK14-A430, was found to penetrate the lipid headgroup structure in pure, ordered-phase DPPC membranes but was located near the headgroup-water region when cholesterol was included. MK14-A430 formed lytic pores in SLBs, and an increase in pore formation with incubation time was observed through an increase in polarity and mobility of the probe. When associated with the Cholesterol-containing SLB, the probe displayed polarity and mobility that indicated a population distributed near the lipid headgroup-water interface with MK14-A430 arranged predominantly in a surface-aligned state. This study indicates that the lytic activity of MK14-A430 occurred through a pore-forming mechanism. The lipid headgroup environment experienced by the fluorescent label, where MK14-A430 displayed pore information, indicated that pore formation was best described by the toroidal pore model.

Lipid Headgroup Charge Controls Melittin Oligomerization in Membranes: Implications in Membrane Lysis

“…These observations are particularly relevant in the context of recent literature challenging the conventional belief that the lytic activity of antimicrobial peptides could be linearly correlated to their affinity for membranes . Instead, emerging paradigms on the interaction of amphipathic peptides with membranes hint at the immense dynamic complexity and transience inherent in these interactions with respect to multiple observables including peptide conformation, , membrane organization, and pathways of membrane destabilization …”