Abstract
Biological membranes are highly dynamic in their ability to orchestrate vital mechanisms including cellular protection, organelle compartmentalization, cellular biomechanics, nutrient transport, molecular/enzymatic recognition, and membrane fusion. Controlling lipid composition of different membranes allows cells to regulate their membrane characteristics, thus modifying their physical properties to permit specific protein interactions and drive structural function (membrane deformation facilitates vesicle budding and fusion) and signal transduction. Yet, how lipids control protein structure and function is still poorly understood and needs systematic investigation. In this review, we explore different in vitro membrane models and summarize our current understanding of the interplay between membrane biophysical properties and lipid–protein interaction, taken as example few proteins involved in muscular activity (dystrophin), digestion and Legionella pneumophila effector protein DrrA. The monolayer model with its movable barriers aims to mimic any membrane deformation while surface pressure modulation imitates lipid packing and membrane curvature changes. It is frequently used to investigate peripheral protein binding to the lipid headgroups. Examples of how lipid lateral pressure modifies protein interaction and organization within the membrane are presented using various biophysical techniques. Interestingly, the shear elasticity and surface viscosity of the monolayer will increase upon specific protein(s) binding, supporting the importance of such mechanical link for membrane stability. The lipid bilayer models such as vesicles are not only used to investigate direct protein binding based on the lipid nature, but more importantly to assess how local membrane curvature (vesicles with different size) influence the binding properties of a protein. Also, supported lipid bilayer model has been used widely to characterize diffusion law of lipids within the bilayer and/or protein/biomolecule binding and diffusion on the membrane. These membrane models continue to elucidate important advances regarding the dynamic properties harmonizing lipid–protein interaction.
Highlights
Biological membranes are fundamental elements for cellular organization
Used in NMR thanks to their ability to align in a magnetic field, they have made it possible to obtain the structure of membrane proteins in their lipid environment, such as that of cytochrome b5, or that of a protein of the HIV virus envelope (Dürr et al, 2007; Dev et al, 2016)
While the membrane proteins are embedded in the bilayer, structural information can be obtained on peripheral proteins when it interacts either with the flat part (Loudet et al, 2005) or with the curved part (Dos Santos Morais et al, 2018)
Summary
Biological membranes are fundamental elements for cellular organization. They provide cellular entities and are responsible for the compartmentalization of cytoplasmic space into functionally specialized organelles as well as controlled exchanges between the interior of the cell and the extracellular environment. The lipids are in a perpetual movement of lateral diffusion, via the Brownian motion (Lipowsky and Sackmann, 1995), and the membrane proteins move, but more slowly than the lipids which surround them With this enormous complexity and huge diversity of lipids; between species and in different membranes in one cell; it is clear that in order to understand the key parameters in the lipid–protein interactions, we are tempted to simplify our experimental conditions, the appearance of basic membrane models. The most well-known and common biomimetic system used for such purposes are discussed here: lipid monolayer, lipid vesicles, and supported lipid bilayers (SLB) with a brief example of bicelles While each of these systems exhibits advantages and disadvantages, it is clear that the exploitation of various model systems and different investigation techniques offers a better understanding of the complex lipid/protein interactions which might be relevant to accomplish membrane functions. Note that proteins that are used here, mainly dystrophin and DrrA, are discussed in depth only to emphasize different examples where lipid biophysical properties modulate lipid–protein interaction
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