The role of hydrophobic and negatively charged surface patches of lipid-free apolipoprotein A-I in lipid binding and ABCA1-mediated cholesterol efflux
The role of hydrophobic and negatively charged surface patches of lipid-free apolipoprotein A-I in lipid binding and ABCA1-mediated cholesterol efflux
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DOI：
10.1016/j.bbalip.2009.09.012
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发表时间：
2010-01-01
影响因子：
4.8
通讯作者：
Davidson, W. Sean
中科院分区：
文献类型：
--
作者：
Smith, Loren E.;Davidson, W. Sean
最近的无脂载脂蛋白a - i模型，包括交联/同源模型和x射线晶体结构，已经在蛋白质表面确定了两个潜在的功能相关的“斑块”。第一个是由亮氨酸残基42、44、46和47组成的疏水表面贴片，第二个是由谷氨酸残基179,191和198组成的带负电荷的贴片。为了确定这些结构域是否发挥功能作用，这些表面斑块被定点诱变破坏，并比较细菌表达的突变体结合脂质和刺激abca1介导的胆固醇外排的能力。研究发现，这两个贴片对apoA-I以abca1依赖的方式接受胆固醇的能力都没有显著的功能作用，但疏水贴片确实影响了apoA-I清除DMPC脂质体的能力。有趣的是，与先前的预测相反，疏水表面斑块的破坏增强了apoA-I的脂质结合能力。疏水表面斑块可能对无脂apoA-I的结构稳定性很重要，或者可能是脂质结合的必要允许结构元件。(C) 2009 Elsevier B.V.版权所有
Recent models of lipid-free apolipoprotein A-I, including a cross-link/homology model and an X-ray crystal structure have identified two potential functionally relevant "patches" on the protein surface. The first is a hydrophobic surface patch composed of leucine residues 42, 44, 46, and 47 and the second a negatively charged patch composed of glutamic acid residues 179,191, and 198. To determine if these domains play a functional role, these surface patches were disrupted by site-directed mutagenesis and the bacterially expressed mutants were compared with respect to their ability to bind lipid and stimulate ABCA1-mediated cholesterol efflux. It was found that neither patch plays a significant functional role in the ability of apoA-I to accept cholesterol in an ABCA1-dependent manner, but that the hydrophobic patch did affect the ability of apoA-I to clear DMPC liposomes. Interestingly, contrary to previous predictions, disruption of the hydrophobic surface patch enhanced the lipid binding ability of apoA-I. The hydrophobic surface patch may be important to the structural stability of lipid-free apoA-I or may be a necessary permissive structural element for lipid binding. (C) 2009 Elsevier B.V. All rights reserved.