Phosphatidylethanolamine enhances the concentration-dependent exchange of phospholipids between bilayers.
It has previously been demonstrated that lipid exchange between phosphatidylcholine vesicles, at higher concentrations, is characterized by a second-order concentration-dependent exchange process in addition to the first-order process operative at lower concentrations (Jones, J. D., & Thompson, T. E. (1989) Biochemistry 28, 129-134). Furthermore, it was demonstrated that the second-order process occurs as a result of an enhancement of the first-order desorption process, possibly resulting from attractive interactions between a potentially desorbing lipid molecule and a transiently apposed bilayer (Jones, J. D., & Thompson, T. E. (1990) Biochemistry 29, 1593-1600). In this work we have studied the exchange of [3H]dimyristoylphosphatidylcholine (DMPC) between large vesicles of the compositions 100% DMPC, 70/30 (mol/mol) DMPC/dimyristoylphosphatidylethanolamine (DMPE), and 68.25/30/1.75 (mol/mol/mol) DMPC/DMPE/dimyristoylphosphatidylglycerol (DMPG). The second-order exchange process is enhanced by 100-fold or more in vesicles containing 30 mol % DMPE relative to 100% DMPC and is reduced or eliminated by the addition of 1.75% of the anionic lipid DMPG. These effects can be achieved by alterations in the equilibrium bilayer separation of 5 A or less. The results are in accord with the model of Jones and Thompson and indicate that relatively low concentrations of PE in a PC bilayer can have significant effects on bilayer surface properties and on potential interactions between bilayers.
Wimley
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WC
Department of Biochemistry, University of Virginia, Charlottesville 22908.
Thompson
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TE
D001692:Biological Transport; D004134:Dimyristoylphosphatidylcholine / Q000378:metabolism; D008051:Lipid Bilayers / Q000378:metabolism*; D010714:Phosphatidylethanolamines / Q000378:metabolism*; D010715:Phosphatidylglycerols / Q000378:metabolism; D010743:Phospholipids / Q000378:metabolism*
D008051:Lipid Bilayers; D010714:Phosphatidylethanolamines; D010715:Phosphatidylglycerols; D010743:Phospholipids; C002773:dimyristoylphosphatidylglycerol; D004134:Dimyristoylphosphatidylcholine