Rye K A, Hime N J, Barter P J
Division of Cardiovascular Services, Royal Adelaide Hospital, Australia.
J Biol Chem. 1995 Jan 6;270(1):189-96. doi: 10.1074/jbc.270.1.189.
The effect of cholesteryl ester transfer protein (CETP) on the size, composition, and structure of spherical, reconstituted HDL (rHDL) which contain apolipoprotein (apo) A-I as their sole apolipoprotein has been studied. Spherical rHDL were incubated with CETP and Intralipid for up to 24 h. During this time CETP promoted transfers of cholesteryl esters (CE) and triglyceride (TG) between rHDL and Intralipid. As a result, the rHDL became depleted of CE and enriched in TG. However, as the loss of CE from the rHDL was greater than the gain of TG, the concentration of core lipids in the rHDL decreased. The decrease in the concentration of rHDL core lipids, which was evident throughout the incubation, was accompanied by a reduction in rHDL diameter from 9.2 to 8.0 nm, the dissociation of apoA-I from rHDL and a decrease in the number of apoA-I molecules, from three/particle in the 9.2-nm rHDL, to two/particle in the 8.0-nm rHDL. Spectroscopic studies showed that the lipid-water interface and phospholipid packing of the 8.0-nm rHDL were, respectively, more polar and less ordered than those of the 9.2-nm rHDL. Quenching studies with KI revealed that the number of exposed apoA-I Trp residues in the 9.2- and 8.0-nm rHDL was two and three, respectively. Circular dichroism established that the 9.2- and 8.0-nm rHDL had identical apoA-I alpha-helical contents. The 9.2- and 8.0-nm rHDL also had identical surface charges as determined by agarose gel electrophoresis. Denaturation studies with guanidine hydrochloride demonstrated that apoA-I is more stable in 8.0-nm rHDL than in 9.2-nm rHDL. It is concluded that CETP converts rHDL to small, TG-enriched, apoA-I-depleted particles with increased lipid-water interfacial hydration and less ordered phospholipid packing. These changes are associated with enhanced stability and minor changes to the conformation of the apoA-I which remains associated with the rHDL.
研究了胆固醇酯转移蛋白（CETP）对以载脂蛋白（apo）A-I作为唯一载脂蛋白的球形重组高密度脂蛋白（rHDL）的大小、组成和结构的影响。将球形rHDL与CETP和英脱利匹特一起孵育长达24小时。在此期间，CETP促进了rHDL与英脱利匹特之间胆固醇酯（CE）和甘油三酯（TG）的转移。结果，rHDL中的CE减少，TG增加。然而，由于rHDL中CE的损失大于TG的增加，rHDL中核心脂质的浓度降低。在整个孵育过程中明显的rHDL核心脂质浓度降低，伴随着rHDL直径从9.2纳米减小到8.0纳米，apoA-I从rHDL解离以及apoA-I分子数量减少，从9.2纳米rHDL中的每个颗粒三个减少到8.0纳米rHDL中的每个颗粒两个。光谱研究表明，8.0纳米rHDL的脂质-水界面和磷脂堆积分别比9.2纳米rHDL更具极性且有序程度更低。用KI进行的猝灭研究表明，9.2纳米和8.0纳米rHDL中暴露的apoA-I色氨酸残基数量分别为两个和三个。圆二色性表明，9.2纳米和8.0纳米rHDL具有相同的apoA-Iα-螺旋含量。通过琼脂糖凝胶电泳测定，9.2纳米和8.0纳米rHDL也具有相同的表面电荷。用盐酸胍进行的变性研究表明，apoA-I在8.0纳米rHDL中比在9.2纳米rHDL中更稳定。得出的结论是，CETP将rHDL转化为富含TG、apoA-I减少的小颗粒，脂质-水界面水合作用增加，磷脂堆积有序程度降低。这些变化与稳定性增强以及与rHDL保持结合的apoA-I构象的微小变化有关。
