COMPUTATIONAL STUDIES ON ORGANELLE-SPECIFIC YEAST MEMBRANE MODELS

Abstract

Computational models were built for the endoplasmic reticulum (ER), trans-Golgi network (TGN), and plasma membranes (PM) of yeast Saccharomyces cerevisiae. Based on experimental data, ergosterol, phosphatidic acid, phosphatidylcholine, phosphatidylethanolamine, phosphatidylserine, and phosphatidylinositol lipids were included. Lipid packing, order parameters (SCD), electron density profiles (EDPs), and lipid rotation were studied for each model. The average surface area per lipid decreased from 63.82±0.03 Å2 in the ER to 47.09±0.12 Å2 at the PM; while the compressibility modulus (KA) varied in opposite direction (PM>TGN>ER). The SCD values were higher (more ordered) for the PM lipids than the ER and TGN membranes by a factor of 1.5. The bilayer thickness estimated from EDPs was larger for the PM (43.9±0.1 Å) than the ER or TGN (37.6±0.1 Å). These properties followed expected experimental trends and were compared against a previous model built by Jo et al. (Biophys J. 2009, 97:50-58).