In vivo roles of BamA, BamB and BamD in the biogenesis of BamA, a core protein of the β-barrel assembly machine of Escherichia coli.
In vivo roles of BamA, BamB and BamD in the biogenesis of BamA, a core protein of the β-barrel assembly machine of Escherichia coli.
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DOI：
10.1016/j.jmb.2014.04.021
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发表时间：
2015-03-13
影响因子：
5.6
通讯作者：
Gabriele R
中科院分区：
文献类型：
--
作者：
Misra R;Stikeleather R;Gabriele R
β-桶状外膜蛋白（OMPs）的组装是革兰氏阴性菌和真核生物的线粒体和叶绿体（细菌起源的两种细胞器）中必不可少的细胞过程。这个过程的核心是属于Omp85超家族的保守β-桶状OMP。在大肠杆菌中，BamA是核心β桶OMP，与4种外膜脂蛋白BamBCDE共同构成β桶组装机（BAM）。本文探讨了必需脂蛋白BamD和BamB在BamA生物发生中的作用。BamD的缺失导致BamA生物发生损伤和细胞生长停止。通过在BamA的β-桶结构域内进行单氨基酸取代定位，可以部分逆转这些缺陷。然而，在缺乏BamB的情况下，在BamD枯竭条件下，β-桶替代对BamA生物发生的积极影响被抵消。通过使用含有其中一种替代的BamA蛋白F494L，证明突变体BamA蛋白不仅可以在没有BamD的情况下组装，而且还可以促进反式表达的野生型BamA的组装。基于这些数据，我们提出了一个模型，其中Bam脂蛋白通过与Bam无关的Lol途径定位于外膜，通过作为新生BamA分子的外膜受体和折叠因子，帮助形成新的Bam复合物。然后，新组装的BAM全息配合物催化底物omp和BamA的组装。这些体内研究结果被最近发表的体外数据所证实。
Assembly of the β-barrel outer membrane proteins (OMPs) is an essential cellular process in Gram negative bacteria and in the mitochondria and chloroplasts of eukaryotes—two organelles of bacterial origin. Central to this process is the conserved β-barrel OMP that belongs to the Omp85 superfamily. In Escherichia coli, BamA is the core β-barrel OMP, and together with four outer membrane lipoproteins, BamBCDE, constitute the β-barrel assembly machine (BAM). In this paper, we investigated the roles of BamD, an essential lipoprotein, and BamB in BamA biogenesis. Depletion of BamD caused impairment in BamA biogenesis and cessation of cell growth. These defects of BamD depletion were partly reversed by single amino acid substitutions mapping within the β-barrel domain of BamA. However, in the absence of BamB, the positive effects of the β-barrel substitutions on BamA biogenesis under BamD depletion conditions were nullified. By employing a BamA protein bearing one such substitution, F494L, it was demonstrated that the mutant BamA protein could not only assemble without BamD, but it could also facilitate the assembly of wild-type BamA expressed in trans. Based on these data, we propose a model in which the Bam lipoproteins, which are localized to the outer membrane by the BAM-independent Lol pathway, aid in the creation of new BAM complexes by serving as outer membrane receptors and folding factors for nascent BamA molecules. The newly assembled BAM holocomplex then catalyzes the assembly of substrate OMPs and BamA. These in vivo findings are corroborated by recently published in vitro data.
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影响因子：
4.8
作者：
Milenkovic, D;Kozjak, V;Meisinger, C
通讯作者：
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