Swenson T L, Brocia R W, Tall A R
Department of Medicine, Columbia University College of Physicians and Surgeons, New York, New York 10032.
J Biol Chem. 1988 Apr 15;263(11):5150-7.
The plasma cholesteryl ester-transfer protein (CETP, Mr 74,000) promotes exchange of both neutral lipids and phospholipids (phosphatidylcholine, PC) between lipoproteins. To investigate the mechanism of facilitated lipid transfer, CETP was incubated with unilamellar egg PC vesicles containing small amounts of cholesteryl ester (CE) or triglyceride, and then analyzed by gel filtration chromatography. There was rapid transfer of radiolabeled CE or triglyceride and PC from vesicles to CETP. The CETP with bound lipids was isolated and incubated with low density lipoproteins (LDL), resulting in transfer of the lipids to LDL. The CETP bound up to 0.9 mol of CE or 0.2 mol of triglyceride and 11 mol of PC/mol of CETP. para-Chloromercuriphenylsulfonate, an inhibitor of CE and triglyceride transfer, was found to decrease the binding of radiolabeled CE and triglyceride by CETP. Under various conditions the CETP eluted either as an apparent monomer with bound lipid (Mr 75,000-93,000), or in complexes with vesicles. The distribution of CETP between these two states was influenced by the presence of apoA-I or albumin, incubation time, vesicle/CETP ratio, and buffer pH and ionic strength. The results indicate that the CETP has binding sites for CE, triglyceride, and PC which readily equilibrate with lipoprotein lipids and suggest that CETP can act as a carrier of lipid between lipoproteins.
血浆胆固醇酯转运蛋白（CETP，分子量74,000）促进脂蛋白之间中性脂质和磷脂（磷脂酰胆碱，PC）的交换。为了研究促进脂质转移的机制，将CETP与含有少量胆固醇酯（CE）或甘油三酯的单层卵PC囊泡一起孵育，然后通过凝胶过滤色谱法进行分析。放射性标记的CE、甘油三酯和PC从囊泡迅速转移到CETP。分离出结合脂质的CETP并与低密度脂蛋白（LDL）一起孵育，导致脂质转移到LDL。CETP每摩尔可结合高达0.9摩尔的CE或0.2摩尔的甘油三酯以及11摩尔的PC。对氯汞苯磺酸盐是CE和甘油三酯转移的抑制剂，发现它可降低CETP对放射性标记的CE和甘油三酯的结合。在各种条件下，CETP要么以结合脂质的表观单体形式洗脱（分子量75,000 - 93,000），要么以与囊泡的复合物形式洗脱。CETP在这两种状态之间的分布受载脂蛋白A - I或白蛋白的存在、孵育时间、囊泡/CETP比率以及缓冲液pH和离子强度的影响。结果表明，CETP具有CE、甘油三酯和PC的结合位点，它们能与脂蛋白脂质迅速达到平衡，这表明CETP可作为脂蛋白之间脂质的载体。
