Cholesterol is abundant in the plasma membranes of animal cells and is known to regulate a variety of membrane properties. Despite decades of research, the transmembrane distribution of cholesterol is still a matter of debate. Here we consider this outstanding issue through atomistic simulations of asymmetric lipid membranes, whose composition is largely consistent with eukaryotic plasma membranes. We show that the membrane dipole potential changes in a cholesterol-dependent manner. Remarkably, moving cholesterol from the extracellular to the cytosolic leaflet increases the dipole potential on the cytosolic side, and vice versa. Biologically this implies that by altering the dipole potential, cholesterol can provide a driving force for cholesterol molecules to favor the cytosolic leaflet, in order to compensate for the intramembrane field that arises from the resting potential.

Belozersky Institute of Physico Chemical Biology Lomonosov Moscow State University Leninskie Gory 1 40 119991 Moscow Russia

Department of Physics Tampere University of Technology P O Box 692 FI 33101 Tampere Finland

Department of Physics University of Helsinki P O Box 64 FI 00014 Helsinki Finland

Faculty of Physics St Petersburg State University Ulyanovskaya str 3 Petrodvorets St Petersburg 198504 Russia

Institute of Macromolecular Compounds Russian Academy of Sciences Bolshoi Prospect 5 O 31 St Petersburg 199004 Russia

Institute of Organic Chemistry and Biochemistry Czech Academy of Sciences Flemingovo náměstí 542 2 166 10 Praha 6 Czech Republic

MEMPHYS Center for Biomembrane Physics University of Southern Denmark Odense Denmark

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