Abstract
The bacterial cell envelope is composed of a mixture of different lipids and proteins, making it an inherently complex organelle. The interactions between integral membrane proteins and lipids are crucial for their respective spatial localization within bacterial cells. We have employed microsecond timescale coarse-grained molecular dynamics simulations of vesicles of varying sizes and with a range of protein and lipid compositions, and used novel approaches to measure both local and global system dynamics, the latter based on spherical harmonics analysis. Our results suggest that both hydrophobic mismatch, enhanced by embedded membrane proteins, and curvature based sorting, due to different modes of undulation, may drive assembly in vesicular systems. Interestingly, the modes of undulation of the vesicles were found to be altered by the specific protein and lipid composition of the vesicle. Strikingly, lipid dynamics were shown to be coupled to proteins up to 6 nm from their surface, a substantially larger distance than has previously been observed, resulting in multi-layered annular rings enriched with particular types of phospholipid. Such large protein-lipid complexes may provide a mechanism for long-range communication. Given the complexity of bacterial membranes, our results suggest that subtle changes in lipid composition may have major implications for lipid and protein sorting under a curvature-based membrane-sorting model.
Highlights
The dynamic behavior of lipids and their interplay with membrane proteins is central to functional organization and compartmentalization within cells and organelles
The current study aimed to investigate role of size, protein content, and lipid composition upon protein association, and the local and global dynamics of lipid vesicles
The results presented here suggest lipid compositions impact both the global and local dynamics of the membrane vesicle
Summary
The dynamic behavior of lipids and their interplay with membrane proteins is central to functional organization and compartmentalization within cells and organelles. Lipid sorting and aggregation of integral membrane proteins can result in a crowded environment, which likely plays a role in structural, mechanical and functional aspects of such membranes. The processes that trigger the spontaneous sorting of these components, and the dependency upon properties such as membrane composition and curvature, are still poorly understood. The combined effects of the overall curvature and local lipid/protein hydrophobic mismatch in cell membranes have been suggested to be key drivers of protein aggregation [1, PLOS ONE | DOI:10.1371/journal.pone.0156963. The combined effects of the overall curvature and local lipid/protein hydrophobic mismatch in cell membranes have been suggested to be key drivers of protein aggregation [1, PLOS ONE | DOI:10.1371/journal.pone.0156963 June 16, 2016
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