Effects of protein oxidation on the structure and stability of model discoidal high-density lipoproteins
Effects of protein oxidation on the structure and stability of model discoidal high-density lipoproteins
复制标题
DOI：
10.1021/bi7023783
复制
发表时间：
2008-03-25
期刊：
影响因子：
2.9
通讯作者：
Gursky, Olga
中科院分区：
文献类型：
--
作者：
Jayaraman, Shobini;Gantz, Donald L.;Gursky, Olga
高密度脂蛋白（HDL）通过清除巨噬细胞中的胆固醇并为低密度脂蛋白提供抗氧化剂来预防动脉粥样硬化。 HDL 的氧化通过涉及多种蛋白质和脂质修饰的复杂机制影响其功能。为了区分 HDL 蛋白质和脂质中氧化修饰的作用，我们分析了次氯酸盐选择性蛋白质氧化 (HOCI) 对由人载脂蛋白（A-I、A-II 或 C-I）和磷脂酰胆碱重构的盘状 HDL 的结构、稳定性和重塑的影响。凝胶电泳和电子显微镜显示，在环境温度下，盘状复合物中的蛋白质氧化促进它们重塑为更大和更小的颗粒。在熔化和动力学实验中通过远紫外圆二色性和光散射监测的热变性表明，蛋白质氧化会使盘状脂蛋白不稳定，并加速蛋白质解折叠、解离和脂蛋白融合。这可能是由于两亲性α-螺旋的脂质结合面中的Met和芳香族残基的氧化以及载脂蛋白在颗粒表面上交联成二聚体和三聚体而导致蛋白质对脂质的亲和力降低。我们得出的结论是，蛋白质氧化会破坏 HDL 盘组装的稳定性，并加速其重塑和融合。这一结果不仅限于模型盘状，还扩展到血浆球形高密度脂蛋白，有助于解释氧化对血浆脂蛋白的复杂影响。
High-density lipoproteins (HDLs) prevent atherosclerosis by removing cholesterol from macrophages and by providing antioxidants for low-density lipoproteins. Oxidation of HDLs affects their functions via the complex mechanisms that involve multiple protein and lipid modifications. To differentiate between the roles of oxidative modifications in HDL proteins and lipids, we analyzed the effects of selective protein oxidation by hypochlorite (HOCI) on the structure, stability, and remodeling of discoidal HDLs reconstituted from human apolipoproteins (A-I, A-II, or C-I) and phosphatidylcholines. Gel electrophoresis and electron microscopy revealed that, at ambient temperatures, protein oxidation in discoidal complexes promotes their remodeling into larger and smaller particles. Thermal denaturation monitored by far-UV circular dichroism and light scattering in melting and kinetic experiments shows that protein oxidation destabilizes discoidal lipoproteins and accelerates protein unfolding, dissociation, and lipoprotein fusion. This is likely due to the reduced affinity of the protein for lipid resulting from oxidation of Met and aromatic residues in the lipid-binding faces of amphipathic a-helices and to apolipoprotein cross-linking into dimers and trimers on the particle surface. We conclude that protein oxidation destabilizes HDL disk assembly and accelerates its remodeling and fusion. This result, which is not limited to model discoidal but also extends to plasma spherical HDL, helps explain the complex effects of oxidation on plasma lipoproteins.