Molecular architecture and dynamics of the plasma membrane lipid bilayer: the red blood cell as a model.
The structural backbone of the erythrocyte membrane, as well as that of any other plasma membrane, is provided by a lipid bilayer which is composed of more than 100 molecular species. The individual lipid classes are distributed over both halves of the bilayer in a highly asymmetric fashion: all glycolipids are exclusively confined to the outer membrane leaflet where we also find the majority of the two choline-containing phospholipids, sphingomyelin and phosphatidylcholine. The two amino-phospholipids are predominantly (phosphatidylethanolamine) or even exclusively (phosphatidylserine) localized in the cytoplasmic half of the bilayer. Glycolipids and sphingomyelin are not subject to transbilayer movements, a property that (under normal conditions) is shared by phosphatidylserine. Phosphatidylcholine exhibits a relatively slow transbilayer movement, revealing half-time values from 3 to 27 h, whereas phosphatidylethanolamine is subject to an ATP-dependent "flippase"-catalyzed inward movement with a half-time of approximately 30 min. Probably much faster than that of any other lipid, is the transbilayer movement of cholesterol, revealing a half-time value in the order of seconds.
Roelofsen
B
B
Department of Lipid Biochemistry, University of Utrecht, The Netherlands.
D001692:Biological Transport; D002784:Cholesterol / Q000737:chemistry / Q000493:pharmacokinetics; D004910:Erythrocyte Membrane / Q000737:chemistry*; D006017:Glycolipids / Q000737:chemistry / Q000493:pharmacokinetics; D006801:Humans; D008051:Lipid Bilayers / Q000737:chemistry* / Q000145:classification / Q000493:pharmacokinetics; D008958:Models, Molecular; D010743:Phospholipids / Q000737:chemistry* / Q000493:pharmacokinetics
D006017:Glycolipids; D008051:Lipid Bilayers; D010743:Phospholipids; D002784:Cholesterol