We previously examined symmetric membrane models for the plasma (PM) and trans-Golgi-network (TGN) membranes of Saccharomyces cerevisiae (yeast). Although diverse in lipid nature and reflecting sterol compositions characteristic to those organelles, our models were not an accurate enough representation as they lacked sphingolipids (SM), relevant for membrane structure and dynamics. Once SM were parametrized for the CHARMM 36 lipid force field, we included them in the new models and added lipid composition asymmetry to better reflect the complexity of these bilayers. The new models include inositol phosphoceramide (IPC) and mannose-(inositol-P)2-ceramide M(IP)2C lipids, both critical in the non-cytosolic leaflets of the PM and TGN. We examined common membrane properties such as surface area per lipid, bilayer thickness, and deuterium order parameters in these models. In addition, studied lipid-lipid interaction and cluster formation between IPC, M(IP)2C and ergosterol, the most common sterol in yeast. The goal of this study is to investigate lipid phase coexistence and leaflet coupling in membrane order and dynamics. Our simulation trajectories add up to 28µs, with two replicate runs for each model run on the Anton and Anton2 machines at the Pittsburgh Supercomputing Center.

Asymmetric models for the trans-Golgi Network and plasma membranes of S. cerevisiae, insights from molecular dynamics

254th National Meeting (2017)

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