Interaction of plasma apolipoproteins with lipid monolayers |
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Authors: | RL Jackson F Pattus RA Demel |
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Institution: | 1. Department of Pharmacology and Cell Biophysics, Biological Chemistry and Medicine, University of Cincinnati College of Medicine, Cincinnati, OH U.S.A.;2. The Biochemical Laboratory, State University of Utrecht, Padualaan 8, Utrecht The Netherlands |
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Abstract: | The monolayer technique has been used to study the interaction of lipids with plasma apolipoproteins. Apolipoprotein C-II and C-III from human very low density lipoproteins, apolipoprotein A-I from human high density lipoproteins and arginine-rich protein from swine very low density lipoproteins were studied. The injection of each apoprotein underneath a monolayer of egg phosphatidyl14C]choline at 20 mN/m caused an increase in surface pressure to approximately 30 mN/m. With apolipoprotein C-II and apolipoprotein C-III there was a decrease in surface radioactivity indicating that the apoproteins were removing phospholipid from the interface; the removal of phospholipid was specific for apolipoprotein C-II and apolipoprotein C-III. Although there was a removal of phospholipid from the monolayer, the surface pressure remained constant and was due to the accumulation of apoprotein at the interface. The rate of surface radioactivity decrease was a function of protein concentration, required lipid in a fluid state and, of the lipids tested, was specific for phosphatidylcholine. Cholesterol and phosphatidylinositol were not removed from the interface. The addition of 33 mol% cholesterol to the phosphatidylcholine monolayer did not affect the removal of phospholipid by apolipoprotein C-III.The addition of phospholipid liposomes to the subphase greatly facilitated the apolipoprotein C-II-mediated removal of phospholipid from the interface. |
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Keywords: | Lipid monolayer Plasma lipoprotein Lipid-protein interaction Lipolysis chylomicrons VLDL LDL HDL To whom reprint requests should be sent |
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