Bacterial outer membrane proteins assemble via asymmetric interactions with the BamA β-barrel
Bacterial outer membrane proteins assemble via asymmetric interactions with the BamA β-barrel
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DOI：
10.1038/s41467-019-11230-9
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发表时间：
2019-07-26
影响因子：
16.6
通讯作者：
Bernstein, Harris D.
中科院分区：
文献类型：
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作者：
Doyle, Matthew T.;Bernstein, Harris D.
β -桶蛋白整合到细菌外膜（OM）是由β -桶组装机制（BAM）催化的。BAM中心亚基（BamA）本身含有一个β -桶结构域，该结构域对OM蛋白的生物发生至关重要，但其作用机制尚不清楚。为了阐明它的功能，我们开发了一种方法，在体内组装的后期捕获天然大肠杆菌β -桶蛋白与BamA稳定结合。使用二硫键交联，我们发现BamA β -桶的横向“开放”形式的第一β -链与底物的c端β -链形成刚性界面。相比之下，最后两条BamA β链的面向脂质的表面与底物的第一条β链形成较弱的构象异质相互作用，可能代表中间组装状态。基于我们的研究结果，我们提出BamA通过“摆动”机制促进部分折叠β -桶的膜整合。
The integration of beta-barrel proteins into the bacterial outer membrane (OM) is catalysed by the beta-barrel assembly machinery (BAM). The central BAM subunit (BamA) itself contains a beta-barrel domain that is essential for OM protein biogenesis, but its mechanism of action is unknown. To elucidate its function, here we develop a method to trap a native Escherichia coli beta-barrel protein bound stably to BamA at a late stage of assembly in vivo. Using disulfide-bond crosslinking, we find that the first beta-strand of a laterally 'open' form of the BamA beta-barrel forms a rigid interface with the C-terminal beta-strand of the substrate. In contrast, the lipid-facing surface of the last two BamA beta-strands forms weaker, conformationally heterogeneous interactions with the first beta-strand of the substrate that likely represent intermediate assembly states. Based on our results, we propose that BamA promotes the membrane integration of partially folded beta-barrels by a 'swing' mechanism.