Jackson R L, Pattus F, Demel R A
Biochim Biophys Acta. 1979 Oct 5;556(3):369-87. doi: 10.1016/0005-2736(79)90126-3.
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 phosphatidy[14C]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 phospholipids 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. Although apolipoprotein A-I and arginine-rich protein gave surface pressure increases, phospholipid was only slightly removed fromthe interface by the addition of liposomes. Based on these findings, we conclude that the apolipoproteins C interact specifically with phosphatidylcholine at the interface. This interaction is important as it relates to the transfer of the apolipoproteins C and phospholipids from very low density lipoproteins to other plasma lipoproteins. The addition of human plasma high density lipoproteins or very low density lipoproteins to the subphase increased the apolipoprotein C-mediated removal of phosphatidyl[14C]choline from the interface 3--4 fold. Low density lipoproteins did not affect the rate of decrease. During lipolysis of very low density lipoproteins to the subphase increased the apolipoprotein C-mediated removal of with the lipid monolayer. Lipolysis experiments were performed in a monolayer trough containing a surface film of egg phosphatidyl[14C]choline and a subphase of very low density lipoproteins and bovine serum albumin. Lipolysis was initiated by the addition of purified milk lipoprotein lipase to the subphase. As a result of lipolysis, there was a decrease in surface radioactivity of phosphatidylcholine. The pre-addition of high density lipoproteins decreased the rate of decrease in surface radioactivity...
单层技术已被用于研究脂质与血浆载脂蛋白的相互作用。对来自人类极低密度脂蛋白的载脂蛋白C-II和C-III、来自人类高密度脂蛋白的载脂蛋白A-I以及来自猪极低密度脂蛋白的富含精氨酸蛋白进行了研究。在20 mN/m的卵磷脂酰[14C]胆碱单层下方注入每种载脂蛋白会使表面压力增加至约30 mN/m。对于载脂蛋白C-II和载脂蛋白C-III，表面放射性降低，这表明载脂蛋白正在从界面去除磷脂；磷脂的去除对载脂蛋白C-II和载脂蛋白C-III具有特异性。尽管从单层中去除了磷脂，但表面压力保持恒定，这是由于载脂蛋白在界面处的积累。表面放射性降低的速率是蛋白质浓度的函数，需要脂质处于流体状态，并且在所测试的脂质中，对磷脂酰胆碱具有特异性。胆固醇和磷脂酰肌醇未从界面去除。向磷脂酰胆碱单层中添加33 mol%的胆固醇并不影响载脂蛋白C-III对磷脂的去除。向亚相添加磷脂脂质体极大地促进了载脂蛋白C-II介导的从界面去除磷脂。尽管载脂蛋白A-I和富含精氨酸蛋白使表面压力增加，但通过添加脂质体仅从界面略微去除了磷脂。基于这些发现，我们得出结论，载脂蛋白C在界面处与磷脂酰胆碱特异性相互作用。这种相互作用很重要，因为它与载脂蛋白C和磷脂从极低密度脂蛋白向其他血浆脂蛋白的转移有关。向亚相添加人类血浆高密度脂蛋白或极低密度脂蛋白使载脂蛋白C介导的从界面去除磷脂酰[14C]胆碱增加了3至4倍。低密度脂蛋白不影响降低速率。在极低密度脂蛋白向亚相的脂解过程中增加了载脂蛋白C介导的与脂质单层的去除。脂解实验在一个单层槽中进行，该槽含有卵磷脂酰[14C]胆碱的表面膜以及极低密度脂蛋白和牛血清白蛋白的亚相。通过向亚相中添加纯化的乳脂蛋白脂肪酶引发脂解。由于脂解作用，磷脂酰胆碱的表面放射性降低。预先添加高密度脂蛋白降低了表面放射性降低的速率……
