Collective Dynamics in Lipid Membranes Containing Transmembrane Peptides

Published

June 21, 2021

Author(s)

Elizabeth Kelley, Paul Butler, Michihiro Nagao

Abstract

Biological membranes are composed of complex mixtures of lipids and proteins that influence each other's structure and function. The biological activities of many channel-forming peptides and proteins are known to depend on the material properties of the surrounding lipid bilayer. However, less is known about how membrane-spanning channels affect the lipid bilayer properties, and in particular, their collective fluctuation dynamics. Here we use neutron spin echo spectroscopy (NSE) to measure the collective bending and thickness fluctuation dynamics in dimyristoylphosphatidylcholine (di 14:0 PC, DMPC) lipid membranes containing two different antimicrobial peptides, alamethicin (Alm) and gramicidin (gD). Alm and gD are both well-studied antimicrobial peptides that form oligomeric membrane-spanning channels with different structures. At low concentrations, the peptides did not have a measurable effect on the average bilayer structure, yet significantly changed the collective membrane dynamics. The two peptides had opposite effects on the relaxation time of the collective bending fluctuations and associated effective bending modulus, with gD increasing and Ala decreasing the rigidity despite both peptides forming transmembrane channels. Meanwhile, the lowest gD concentrations enhanced the collective thickness fluctuation dynamics, while the higher gD concentrations and all studied Ala concentrations dampened these dynamics. The results highlight the synergy between lipids and proteins in determining the collective membrane dynamics and that not all peptides can be universally treated as rigid bodies when considering their effects on the lipid bilayer fluctuations.

Citation

Soft Matter

Volume

17

Issue

23

Pub Type

Journals

Keywords

membrane dynamics, lipid bilayers, transmembrane peptide, antimicrobial peptide, bending stiffness, thickness fluctuations

Citation

Kelley, E. , Butler, P. and Nagao, M. (2021), Collective Dynamics in Lipid Membranes Containing Transmembrane Peptides, Soft Matter (Accessed November 23, 2024)