Bakelar Jeremy, Buchanan Susan K, Noinaj Nicholas
Markey Center for Structural Biology, Department of Biological Sciences, Purdue University, West Lafayette, IN 47907, USA.
National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892, USA.
Science. 2016 Jan 8;351(6269):180-6. doi: 10.1126/science.aad3460.
β-Barrel outer membrane proteins (OMPs) are found in the outer membranes of Gram-negative bacteria and are essential for nutrient import, signaling, and adhesion. A 200-kilodalton five-component complex called the β-barrel assembly machinery (BAM) complex has been implicated in the biogenesis of OMPs. We report the structure of the BAM complex from Escherichia coli, revealing that binding of BamCDE modulates the conformation of BamA, the central component, which may serve to regulate the BAM complex. The periplasmic domain of BamA was in a closed state that prevents access to the barrel lumen, which indicates substrate OMPs may not be threaded through the barrel during biogenesis. Further, conformational shifts in the barrel domain lead to opening of the exit pore and rearrangement at the lateral gate.
β-桶状外膜蛋白（OMPs）存在于革兰氏阴性菌的外膜中，对于营养物质的输入、信号传导和黏附至关重要。一种名为β-桶组装机器（BAM）复合体的200千道尔顿五组分复合体与OMPs的生物合成有关。我们报道了来自大肠杆菌的BAM复合体的结构，揭示了BamCDE的结合调节了核心组分BamA的构象，这可能用于调节BAM复合体。BamA的周质结构域处于封闭状态，阻止进入桶腔，这表明底物OMPs在生物合成过程中可能不会穿过桶。此外，桶结构域的构象变化导致出口孔打开和侧门重排。
