Structure and activity of lipid bilayer within a membrane-protein transporter
Structure and activity of lipid bilayer within a membrane-protein transporter
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DOI：
10.1073/pnas.1812526115
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发表时间：
2018-12-18
影响因子：
11.1
通讯作者：
Guo, Youzhong
中科院分区：
文献类型：
--
作者：
Qiu, Weihua;Fu, Ziao;Guo, Youzhong
膜蛋白在天然细胞膜中起作用，但在许多生化和结构分析中需要提取成分离的颗粒。常用的洗涤剂提取方法会破坏天然相关的脂质双分子层。在这里，我们设计了一种无洗涤剂的方法来制备细胞膜纳米颗粒，以研究多药物出口AcrB，通过低温电镜在3.2-A分辨率。我们发现了与AcrB三聚体跨膜结构域相关的组织良好的脂质双分子层结构。该双层贴片由24个脂质分子组成；内部小叶链以六角形排列排列，而外部小叶具有高度不规则但有序的排列。蛋白质侧链与两个小叶相互作用并参与六边形图案。我们认为脂质双分子层通过AcrB三聚体支持和协调蠕动运动。在AcrB D407A中，一个假定的质子接力突变体，脂质双分子层支持在清洁剂溶解后晶体结构中丢失的蛋白质相互作用。我们的无洗涤剂系统保留了脂质-蛋白质相互作用的可视化，应该广泛适用。
Membrane proteins function in native cell membranes, but extraction into isolated particles is needed for many biochemical and structural analyses. Commonly used detergent-extraction methods destroy naturally associated lipid bilayers. Here, we devised a detergent-free method for preparing cell-membrane nanoparticles to study the multidrug exporter AcrB, by cryo-EM at 3.2-A resolution. We discovered a remarkably well-organized lipid-bilayer structure associated with transmembrane domains of the AcrB trimer. This bilayer patch comprises 24 lipid molecules; inner leaflet chains are packed in a hexagonal array, whereas the outer leaflet has highly irregular but ordered packing. Protein side chains interact with both leaflets and participate in the hexagonal pattern. We suggest that the lipid bilayer supports and harmonizes peristaltic motions through AcrB trimers. In AcrB D407A, a putative proton-relay mutant, lipid bilayer buttresses protein interactions lost in crystal structures after detergent-solubilization. Our detergent-free system preserves lipid-protein interactions for visualization and should be broadly applicable.