Native Mass Spectrometry, Ion Mobility, Electron-Capture Dissociation, and Modeling Provide Structural Information for Gas-Phase Apolipoprotein E Oligomers.
Native Mass Spectrometry, Ion Mobility, Electron-Capture Dissociation, and Modeling Provide Structural Information for Gas-Phase Apolipoprotein E Oligomers.
复制标题
天然质谱、离子淌度、电子捕获解离和建模提供了气相载脂蛋白 E 寡聚物的结构信息。
DOI：
10.1007/s13361-019-02148-z
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发表时间：
2019
影响因子：
3.2
通讯作者：
Gross,MichaelL
中科院分区：
文献类型：
--
作者：
Wang,Hanliu;Eschweiler,Joseph;Cui,Weidong;Zhang,Hao;Frieden,Carl;Ruotolo,BrandonT;Gross,MichaelL
载脂蛋白E（apoE）是脂质和胆固醇代谢中的必需蛋白。虽然人类中三种常见的同种型仅在两个位点上不同，但它们在阿尔茨海默病（AD）中的后果却截然不同：只有ε4等位基因是迟发性阿尔茨海默病的主要遗传风险因素。在无脂质环境中，亚型以低μM浓度的低聚物（主要是四聚体）混合物形式存在。这种自缔合参与与无脂质状态的平衡，并且寡聚化界面与脂质结合区域重叠。然而，在寡聚状态下的apoE野生型（WT）结构的阐明尚未实现。为了满足这一需求，我们使用了天然电喷雾电离和质谱（天然MS）结合离子迁移率（IM）来检查三种WT亚型的单体和四聚体。虽然碰撞诱导的解折叠（CIU）不能区分野生型异构体，单体突变体（MM）的apoE 3表现出更高的稳定性时，提交CIU比野生型单体。从离子迁移率的测量，我们得到的碰撞截面，并建立了一个粗粒度模型的四聚体。应用电子捕获解离（ECD）的四聚体的原因展开从C-末端结构域，在良好的协议与解决方案变性数据，并提供了额外的支持C4对称结构的四聚体。
Apolipoprotein E (apoE) is an essential protein in lipid and cholesterol metabolism. Although the three common isoforms in humans differ only at two sites, their consequences in Alzheimer’s disease (AD) are dramatically different: only theε4 allele is a major genetic risk factor for late-onset Alzheimer’s disease. The isoforms exist as a mixture of oligomers, primarily tetramer, at low μM concentrations in a lipid-free environment. This self-association is involved in equilibrium with the lipid-free state, and the oligomerization interface overlaps with the lipid-binding region. Elucidation of apoE wild-type (WT) structures at an oligomeric state, however, has not yet been achieved. To address this need, we used native electrospray ionization and mass spectrometry (native MS) coupled with ion mobility (IM) to examine the monomer and tetramer of the three WT isoforms. Although collision-induced unfolding (CIU) cannot distinguish the WT isoforms, the monomeric mutant (MM) of apoE3 shows higher stability when submitted to CIU than the WT monomer. From ion-mobility measurements, we obtained the collision cross section and built a coarse-grained model for the tetramer. Application of electron-capture dissociation (ECD) to the tetramer causes unfolding starting from the C-terminal domain, in good agreement with solution denaturation data, and provides additional support for the C4 symmetry structure of the tetramer.