Shen Chongrong, Chang Shenghai, Luo Qinghua, Chan Kevin Chun, Zhang Zhibo, Luo Bingnan, Xie Teng, Lu Guangwen, Zhu Xiaofeng, Wei Xiawei, Dong Changjiang, Zhou Ruhong, Zhang Xing, Tang Xiaodi, Dong Haohao
State Key Laboratory of Biotherapy and Cancer Center, National Clinical Research Center for Geriatrics, West China Hospital, Sichuan University and Collaborative Innovation Center of Biotherapy, Chengdu, China.
Department of Biophysics of Sir Run Run Shaw Hospital, Zhejiang University School of Medicine, Hangzhou, China.
Nature. 2023 May;617(7959):185-193. doi: 10.1038/s41586-023-05988-8. Epub 2023 Apr 26.
The outer membrane structure is common in Gram-negative bacteria, mitochondria and chloroplasts, and contains outer membrane β-barrel proteins (OMPs) that are essential interchange portals of materials. All known OMPs share the antiparallel β-strand topology, implicating a common evolutionary origin and conserved folding mechanism. Models have been proposed for bacterial β-barrel assembly machinery (BAM) to initiate OMP folding; however, mechanisms by which BAM proceeds to complete OMP assembly remain unclear. Here we report intermediate structures of BAM assembling an OMP substrate, EspP, demonstrating sequential conformational dynamics of BAM during the late stages of OMP assembly, which is further supported by molecular dynamics simulations. Mutagenic in vitro and in vivo assembly assays reveal functional residues of BamA and EspP for barrel hybridization, closure and release. Our work provides novel insights into the common mechanism of OMP assembly.
外膜结构在革兰氏阴性菌、线粒体和叶绿体中很常见，并且包含外膜β桶蛋白（OMPs），这些蛋白是物质的重要交换通道。所有已知的OMPs都具有反平行β链拓扑结构，这意味着它们有共同的进化起源和保守的折叠机制。已经提出了细菌β桶组装机器（BAM）启动OMP折叠的模型；然而，BAM完成OMP组装的机制仍不清楚。在这里，我们报告了BAM组装OMP底物EspP的中间结构，展示了在OMP组装后期BAM的连续构象动力学，分子动力学模拟进一步支持了这一点。体外和体内诱变组装试验揭示了BamA和EspP在桶杂交、封闭和释放方面的功能残基。我们的工作为OMP组装的共同机制提供了新的见解。
