Bilayer membrane destabilization induced by dolichylphosphate.
Small vesicles containing the fluorescent probe calcein were used to investigate the effect of dolichyl phosphate (Dol-P) on phospholipid bilayer stability. In the absence of Dol-P, phospholipid vesicles retained the fluorescent probe upon the addition of divalent cations. Small vesicles containing Dol-P, however, exhibited calcein leakage when incubated in the presence of divalent cations. This effect was observed in liposomes composed of a mixture of phosphatidylethanolamine (PE), phosphatidylcholine (PC) and Dol-P, but not in PC/Dol-P liposomes. The rate of calcein leakage was proportional to divalent cation concentration and to temperature, but was independent of vesicle concentration. These results demonstrate that Dol-P has significant effects on the stability of PE containing phospholipid bilayers. Vesicle leakage was also promoted by the addition of rat liver Dol-P-mannose synthase (EC 2.4.1.83) to intact PE/PC/Dol-P vesicles. Enzyme induced leakage from phospholipid vesicles required the presence of both unsaturated PE and Dol-P. The phospholipid composition of leaky vesicles could be correlated with the lipid matrix required for maximal transferase activity of the rat liver synthase. The destabilizing effects of Dol-P on phospholipid bilayers may therefore be involved in the translocation of activated sugars across biological membranes.
Schutzbach
J S
JS
Department of Microbiology, University of Alabama, Birmingham 35294.
Jensen
J W
JW
D000818:Animals; D002413:Cations, Divalent; D004288:Dolichol Phosphates / Q000378:metabolism; D005452:Fluoresceins; D066298:In Vitro Techniques; D008051:Lipid Bilayers / Q000378:metabolism; D008364:Mannosyltransferases / Q000378:metabolism; D010713:Phosphatidylcholines; D010714:Phosphatidylethanolamines; D011106:Polyisoprenyl Phosphates / Q000378:metabolism; D051381:Rats
D002413:Cations, Divalent; D004288:Dolichol Phosphates; D005452:Fluoresceins; D008051:Lipid Bilayers; D010713:Phosphatidylcholines; D010714:Phosphatidylethanolamines; D011106:Polyisoprenyl Phosphates; C028306:dolichol monophosphate; D008364:Mannosyltransferases; C022755:dolichyl-phosphate beta-D-mannosyltransferase; C007740:fluorexon