Effects of polymorphism on the lipid interaction of human apolipoprotein E
Effects of polymorphism on the lipid interaction of human apolipoprotein E
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DOI：
10.1074/jbc.m304814200
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发表时间：
2003-10-17
影响因子：
4.8
通讯作者：
Lund-Katz, S
中科院分区：
文献类型：
--
作者：
Saito, H;Dhanasekaran, P;Lund-Katz, S
ApoE以三种常见的同种型存在，apoE 2、apoE 3和apoE 4; apoE 2和apoE 3优先结合高密度脂蛋白，而apoE 4优先结合极低密度脂蛋白（VLDL）。为了了解这些亚型在人血浆中不同脂蛋白分布的分子基础，我们使用脂肪乳剂检查了apoE亚型和一些突变体的脂质结合特性。对于大（120 nm）和小（35 nm）乳剂颗粒，apoE 4的结合亲和力远高于apoE 2和apoE 3，而三种亚型之间的最大结合能力相似。22-kDa的N-末端片段的apoE 4显示出更高的结合能力比apoE 2和apoE 3。apoE 4（E255 A）突变体在Arg（61）和Glu（255）之间没有静电相互作用，显示出与apoE 3类似的结合行为，表明apoE 4中的N-和C-末端结构域相互作用是其对脂质的高亲和力的原因。此外，apoE 3（P267 A）突变体，这是假定含有一个长的α-螺旋在C-末端结构域，有显着降低的结合能力，两种大小的乳液颗粒，这表明apoE 4的VLDL的偏好是不是由于一个稳定的长α-螺旋结构。等温滴定量热法的测量结果表明，有没有显着差异的apoE异构体之间的乳液结合的热力学参数。然而，8-苯胺基-1-萘磺酸结合apoE的荧光测量表明，apoE 4具有更多的暴露的疏水表面相比，apoE 3，主要是由于不同的三级组织的C-末端结构域。apoE 4的C-末端结构域中较少的组织结构导致对脂质的较高亲和力，有助于其优先与VLDL结合。事实上，我们发现apoE 4与VLDL的结合亲和力高于apoE 3。
ApoE exists as three common isoforms, apoE2, apoE3, and apoE4; apoE2 and apoE3 preferentially bind to high density lipoproteins, whereas apoE4 prefers very low density lipoproteins ( VLDL). To understand the molecular basis for the different lipoprotein distributions of these isoforms in human plasma, we examined the lipid- binding properties of the apoE isoforms and some mutants using lipid emulsions. With both large ( 120 nm) and small ( 35 nm) emulsion particles, the binding affinity of apoE4 was much higher than that of apoE2 and apoE3, whereas the maximal binding capacities were similar among the three isoforms. The 22-kDa N-terminal fragment of apoE4 displayed a much higher binding capacity than did apoE2 and apoE3. The apoE4(E255A) mutant, which has no electrostatic interaction between Arg(61) and Glu(255), showed binding behavior similar to that of apoE3, indicating that N- and C-terminal domain interaction in apoE4 is responsible for its high affinity for lipid. In addition, the apoE3( P267A) mutant, which is postulated to contain a long alpha-helix in the C-terminal domain, had significantly decreased binding capacities for both sizes of emulsion particle, suggesting that the apoE4 preference for VLDL is not due to a stabilized long alpha-helical structure. Isothermal titration calorimetry measurements showed that there is no significant difference in thermodynamic parameters for emulsion binding among the apoE isoforms. However, fluorescence measurements of 8-anilino-1-naphthalenesulfonic acid binding to apoE indicated that apoE4 has more exposed hydrophobic surface compared with apoE3 mainly due to the different tertiary organization of the C-terminal domain. The less organized structure in the C-terminal domain of apoE4 leads to the higher affinity for lipid, contributing to its preferential association with VLDL. In fact, we found that apoE4 binds to VLDL with higher affinity compared with apoE3.