Crystal Structure of Escherichia coli BamB, a Lipoprotein Component of the β-Barrel Assembly Machinery Complex
Crystal Structure of Escherichia coli BamB, a Lipoprotein Component of the β-Barrel Assembly Machinery Complex
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DOI：
10.1016/j.jmb.2010.12.020
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发表时间：
2011-03-11
影响因子：
5.6
通讯作者：
Paetzel, Mark
中科院分区：
文献类型：
--
作者：
Kim, Kelly H.;Paetzel, Mark
在革兰氏阴性菌中，BAM（β-桶装配机）复合物催化装配外膜蛋白的基本过程。大肠杆菌中的BAM复合物由五种蛋白质组成：一种β桶膜蛋白BamA和四种脂蛋白BamB、BamC、BamD和BamE。尽管它们在外膜蛋白生物合成中的作用，但目前缺乏BAM复合物的脂蛋白组分的功能和结构信息。在这里，我们报告的第一个晶体结构的BamB，最大的和功能最突出的脂蛋白组分的BAM复合物。晶体结构显示BamB具有八叶片β螺旋桨结构，每个叶片由四条β链组成。映射到结构上的残基先前显示是重要的BamA相互作用揭示，这些残基，尽管是相距甚远的氨基酸序列，被本地化，形成一个连续的溶剂暴露的表面上的一侧的β-螺旋桨。在β-螺旋桨的同一侧发现了一组在BamB同源物中保守的残基。有趣的是，我们的结构比较研究表明，其他具有BamB样折叠的蛋白质通常参与蛋白质或配体结合，并且这些蛋白质上的结合界面位于BamB上发现的保守残基和对BamA相互作用重要的残基在拓扑上等同的表面上。我们的结构和生物信息学分析，加上以前的生化数据，提供了线索，BamA和可能的基板相互作用界面可能位于BamB。(C)2010爱思唯尔有限公司保留所有权利。
In Gram-negative bacteria, the BAM (beta-barrel assembly machinery) complex catalyzes the essential process of assembling outer membrane proteins. The BAM complex in Escherichia coli consists of five proteins: one beta-barrel membrane protein, BamA, and four lipoproteins, BamB, BamC, BamD, and BamE. Despite their role in outer membrane protein biogenesis, there is currently a lack of functional and structural information on the lipoprotein components of the BAM complex. Here, we report the first crystal structure of BamB, the largest and most functionally characterized lipoprotein component of the BAM complex. The crystal structure shows that BamB has an eight-bladed beta-propeller structure, with four beta-strands making up each blade. Mapping onto the structure the residues previously shown to be important for BamA interaction reveals that these residues, despite being far apart in the amino acid sequence, are localized to form a continuous solvent-exposed surface on one side of the beta-propeller. Found on the same side of the beta-propeller is a cluster of residues conserved among BamB homologs. Interestingly, our structural comparison study suggests that other proteins with a BamB-like fold often participate in protein or ligand binding, and that the binding interface on these proteins is located on the surface that is topologically equivalent to where the conserved residues and the residues that are important for BamA interaction are found on BamB. Our structural and bioinformatic analyses, together with previous biochemical data, provide clues to where the BamA and possibly a substrate interaction interface may be located on BamB. (C) 2010 Elsevier Ltd. All rights reserved.