MOLECULAR PACKING OF HIGH-DENSITY AND LOW-DENSITY LIPOPROTEIN SURFACE-LIPIDS AND APOLIPOPROTEIN A-I BINDING
MOLECULAR PACKING OF HIGH-DENSITY AND LOW-DENSITY LIPOPROTEIN SURFACE-LIPIDS AND APOLIPOPROTEIN A-I BINDING
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DOI：
10.1021/bi00429a029
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发表时间：
1989-02-07
期刊：
影响因子：
2.9
通讯作者：
PHILLIPS, MC
中科院分区：
文献类型：
--
作者：
IBDAH, JA;LUNDKATZ, S;PHILLIPS, MC
表面压力（π）-使用人高密度脂蛋白（HDL 3）和低密度脂蛋白（LDL）磷脂的单层以及这些磷脂的混合单层的分子面积（A）等温线，其中胆固醇在空气-水界面上扩散，以推断HDL 3和LDL颗粒表面上可能的分子堆积。LDL磷脂比HDL 3磷脂形成更致密的单层;例如，LDL和HDL 3磷脂在π. = 10达因/厘米时，分别为88和75埃2/分子。低密度脂蛋白磷脂单层中的紧密堆积可归因于饱和磷脂酰胆碱和鞘磷脂的含量高于高密度脂蛋白3。胆固醇使HDL 3和LDL磷脂单层都凝结，但对LDL磷脂单层有更大的凝结作用。. pi. - HDL 3磷脂胆固醇和LDL磷脂/胆固醇的混合单层的等温线在化学计量上类似于脂蛋白颗粒表面的等温线，表明LDL颗粒表面的单层比HDL 3颗粒表面的单层明显更致密。LDL中更紧密的侧向堆积至少是由于三个因素：（1）磷脂组成的差异;（2）LDL中更高的未酯化胆固醇含量;和（3）胆固醇和LDL磷脂之间的相互作用相对于HLD 3磷脂更强。通过监测14 C-甲基化的apo A-I对在各种初始表面压力（π i）下铺展的这些脂质的单层的吸附，评价脂质分子堆积对人载脂蛋白A-I（apo A-I）对HDL 3和LDL表面脂质的亲和力的影响。在给定的（π i）下，apo A-I吸附到HDL 3表面脂质单层比吸附到LDL表面脂质单层更多，并且在π i ≥时不能吸附到HDL 3和LDL表面脂质单层。26和20达因/厘米。胆固醇通常会降低载脂蛋白A-I对脂蛋白表面脂质单层的吸附。这些研究表明，脂蛋白颗粒表面的分子堆积影响载脂蛋白A-I的结合，并且LDL的表面脂质组成至少部分是体内LDL颗粒中缺乏载脂蛋白A-I的原因。
The surface pressure (.pi.)-molecular area (A) isotherms for monolayers of human high-density lipoprotein (HDL3) and low-density lipoprotein (LDL) phospholipids and of mixed monolayers of these phospholipids with cholesterol spread at the air-water interface were used to deduce the likely molecular packing at the surfaces of HDL3 and LDL particles. LDL phospholipids form more condensed monolayers than HDL3 phospholipids; for example, the molecular areas of LDL and HDL3 phospholipids at .pi. = 10 dyn/cm are 88 and 75 .ANG.2/molecule, respectivley. The closer packing in the LDL phospholipid monolayer can be attributed to the higher contents of saturated phosphatidylcholines an sphingomyelin relative to HDL3. Cholesterol condenses both HDL3 and LDL phospholipid monolayers but has a greater condensing effect on the LDL phospholipid monolayer. The .pi.-A isotherms for mixed monolayers of HDL3 phospholipid cholesterol and LDL phospholipid/cholesterol at stoichiometries similar to those at the surfaces of lipoprotein particles suggest that the monolayer at the surface of the LDL particle is significantly more condensed than that at the surface of the HDL3 particle. The closer lateral packing in LDL is due to at least three factors: (1) the difference in phospholipid composition; (2) the higher unesterified cholesterol content in LDL; and (3) a stronger interaction between cholesterol and LDL phospholipids relative to HLD3 phospholipids. The influence of lipid molecular packing on the affintiy of human apolipoprotein A-I (apo A-I) for HDL3 and LDL surface lipids was evaluated by monitoring the adsorption of 14C-methylated apo A-I to monolayers of these lipids spread at various initial surface pressures (.pi.i). At a given (.pi.i), apo A-I adsorbs more to the HDL3 surface lipid monolayer than to the LDL surface lipid monolayer and fails to adsorb to the HDL3 and LDL surface lipid monolayers at .pi.i .gtoreq. 26 and 20 dyn/cm, respectively. Cholesterol generally decreases the adsorption of apo A-I to the lipoprotein surface lipid monolayers. These studies suggest that the molecular packing at the surface of lipoprotein particles influences the binding of apo A-I and that the surface lipid composition of LDL is, at least partially, the reason for the absence of apo A-I in LDL particles in vivo.