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 1-3 . All known OMPs share the antiparallel β-strand topology 4 , implicating a common evolutionary origin and conserved folding mechanism. Models have been proposed for bacterial β-barrel assembly machinery (BAM) to initiate OMP folding 5,6 ; 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.
Organizational Affiliation:
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.
Center of Cryo Electron Microscopy, Zhejiang University, Hangzhou, China.
Liangzhu Laboratory, Zhejiang University Medical Center, Hangzhou, China.
Department of Pathology of Sir Run Run Shaw Hospital, Zhejiang University School of Medicine, Hangzhou, China.
Frontiers Medical Center, Tianfu Jincheng Laboratory, West China Hospital, Sichuan University, Chengdu, China.
Institute of Quantitative Biology, College of Life Sciences, Cancer Center, The First Affiliated Hospital, School of Medicine, Zhejiang University, Hangzhou, China.
Shanghai Institute for Advanced Study, Zhejiang University, Shanghai, China.
College of Life Science, Sichuan University, Chengdu, China.
School of Pharmaceutical Sciences, Wuhan University, Wuhan, China.
Institute of Quantitative Biology, College of Life Sciences, Cancer Center, The First Affiliated Hospital, School of Medicine, Zhejiang University, Hangzhou, China. rhzhou@zju.edu.cn.
Shanghai Institute for Advanced Study, Zhejiang University, Shanghai, China. rhzhou@zju.edu.cn.
Department of Chemistry, Columbia University, New York, NY, USA. rhzhou@zju.edu.cn.
Department of Biophysics of Sir Run Run Shaw Hospital, Zhejiang University School of Medicine, Hangzhou, China. xzhang1999@zju.edu.cn.
Center of Cryo Electron Microscopy, Zhejiang University, Hangzhou, China. xzhang1999@zju.edu.cn.
Liangzhu Laboratory, Zhejiang University Medical Center, Hangzhou, China. xzhang1999@zju.edu.cn.
Department of Pathology of Sir Run Run Shaw Hospital, Zhejiang University School of Medicine, Hangzhou, China. xzhang1999@zju.edu.cn.
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. tangxiaodi@scu.edu.cn.
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. haohaodong@scu.edu.cn.
Department of Pathology of Sir Run Run Shaw Hospital, Zhejiang University School of Medicine, Hangzhou, China. haohaodong@scu.edu.cn.
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