A minimalist model lipid system mimicking the biophysical properties ofEscherichia coli’smembrane

Abstract

Biological membrane are highly complex systems that are of fundamental importance to the development and survival of organisms. Native membranes typically comprise different types of lipids, biomolecules and proteins assembled around a lipid bilayer structure. This complexity can render investigations challenging, with many studies relying on model membranes such as artificial vesicles and supported lipid bilayers (SLBs). The purpose of a model system is to capture the desired dominant features of the native context while remaining uniquely defined and simpler. Here, we search for a minimal lipid-only model system of the Escherichia coli inner membrane. We aim to retain the main lipidomic components in their native ratio while mimicking the membrane thermal and mechanical properties. We design a collection of candidate model systems reflecting the main aspects of the known native lipidomic composition and narrow down our selection based on the systems phase transition temperature. We further test our candidate model systems by independently measuring their elastic properties. We identify 3 ternary model systems able to form stable bilayers that closely mimic E. coli inner membrane lipid composition and mechanical properties. These model systems are made of commercially available synthetic 16:0-18:1 phosphatidylethanolamine (POPE), 16:0-18:1 phosphatidylglycerol (POPG), and 16:0-18:1 Cardiolipin (CL). We anticipate our results to be of interest for future studies making use of E. coli models, for example investigating membrane proteins function or macromolecule-membrane interactions.