Apolar Polyisoprenoids Located in the Midplane of the Bilayer Regulate the Response of an Archaeal-Like Membrane to High Temperature and Pressure.

Philippe M Oger,Judith Peters,Marta Salvador-Castell,Bruno Demé,Josephine G Loricco

doi:10.3389/fchem.2020.594039

Abstract

Archaea are known to inhabit some of the most extreme environments on Earth. The ability of archaea possessing membrane bilayers to adapt to high temperature (>85°C) and high pressure (>1,000 bar) environments is proposed to be due to the presence of apolar polyisoprenoids at the midplane of the bilayer. In this work, we study the response of this novel membrane architecture to both high temperature and high hydrostatic pressure using neutron diffraction. A mixture of two diether, phytanyl chain lipids (DoPhPC and DoPhPE) and squalane was used to model this novel architecture. Diffraction data indicate that at high temperatures a stable coexistence of fluid lamellar phases exists within the membrane and that stable coexistence of these phases is also possible at high pressure. Increasing the amount of squalane in the membrane regulates the phase separation with respect to both temperature and pressure, and also leads to an increase in the lamellar repeat spacing. The ability of squalane to regulate the ultrastructure of an archaea-like membrane at high pressure and temperature supports the hypothesis that archaea can use apolar lipids as an adaptive mechanism to extreme conditions.

Highlights

According to the Singer-Nicolson model, cell membranes are composed of a “mosaic” of proteins embedded in a fluid, lipid bilayer (Singer and Nicolson, 1972)
In order to probe how this membrane behaves under the extreme conditions of temperature and pressure faced by archaea, neutron diffraction was performed on oriented stacked bilayers at temperatures up to 85◦C and pressures up to 1,000 bar
The aims of this study were to determine how an archaeal-like membrane with this novel membrane architecture behaves in response to the high temperatures and high hydrostatic pressures and to determine how the quantity of apolar lipid present in the membrane modulates this behavior

Summary

Introduction

According to the Singer-Nicolson model, cell membranes are composed of a “mosaic” of proteins embedded in a fluid, lipid bilayer (Singer and Nicolson, 1972). Domains are laterally organized membrane regions with distinct lipid compositions and specialized functions such as interacting with specific proteins, or adopting a specific curvature (Tayebi et al, 2012; Arumugam and Bassereau, 2015; Marquardt et al, 2015). Such lateral membrane domains have been well-characterized in eukaryotic and bacterial cells (Baumgart et al, 2003; Heberle and Feigenson, 2011; Heberle et al, 2013; McCarthy et al, 2015; Schmid, 2017)

Methods

Results

Conclusion