title: Structural basis of outer membrane protein insertion by the BAM complex.
abstract: All Gram-negative bacteria, mitochondria and chloroplasts have outer membrane proteins (OMPs) that perform many fundamental biological processes. The OMPs in Gram-negative bacteria are inserted and folded into the outer membrane by the β-barrel assembly machinery (BAM). The mechanism involved is poorly understood, owing to the absence of a structure of the entire BAM complex. Here we report two crystal structures of the Escherichia coli BAM complex in two distinct states: an inward-open state and a lateral-open state. Our structures reveal that the five polypeptide transport-associated domains of BamA form a ring architecture with four associated lipoproteins, BamB-BamE, in the periplasm. Our structural, functional studies and molecular dynamics simulations indicate that these subunits rotate with respect to the integral membrane β-barrel of BamA to induce movement of the β-strands of the barrel and promote insertion of the nascent OMP.
authors.affiliation: Biomedical Research Centre, Norwich Medical School, University of East Anglia, Norwich Research Park, Norwich NR4 7TJ, UK.
authors.forename: Yinghong
authors.initials: Y
authors.lastname: Gu
authors.affiliation: Biomedical Research Centre, Norwich Medical School, University of East Anglia, Norwich Research Park, Norwich NR4 7TJ, UK.
authors.forename: Huanyu
authors.initials: H
authors.lastname: Li
authors.affiliation: Biomedical Research Centre, Norwich Medical School, University of East Anglia, Norwich Research Park, Norwich NR4 7TJ, UK.
authors.forename: Haohao
authors.initials: H
authors.lastname: Dong
authors.affiliation: Biomedical Research Centre, Norwich Medical School, University of East Anglia, Norwich Research Park, Norwich NR4 7TJ, UK.
authors.forename: Yi
authors.initials: Y
authors.lastname: Zeng
authors.affiliation: Biomedical Research Centre, Norwich Medical School, University of East Anglia, Norwich Research Park, Norwich NR4 7TJ, UK.
authors.forename: Zhengyu
authors.initials: Z
authors.lastname: Zhang
authors.affiliation: Diamond Light Source, Harwell Science and Innovation Campus, Didcot, Oxfordshire OX11 0DE, UK.
authors.forename: Neil G
authors.initials: NG
authors.lastname: Paterson
authors.affiliation: Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, UK.
authors.forename: Phillip J
authors.initials: PJ
authors.lastname: Stansfeld
authors.affiliation: Biomedical Research Centre, Norwich Medical School, University of East Anglia, Norwich Research Park, Norwich NR4 7TJ, UK.|Jiangsu Province Key Laboratory of Anesthesiology, Xuzhou Medical College, Xuzhou 221004, China.|Key Laboratory of Bio-resources and Eco-environment, Ministry of Education, Sichuan Key Laboratory of Molecular Biology and Biotechnology, College of Life Sciences, Sichuan University, Chengdu 610064, China.
authors.forename: Zhongshan
authors.initials: Z
authors.lastname: Wang
authors.affiliation: Key Laboratory of Bio-resources and Eco-environment, Ministry of Education, Sichuan Key Laboratory of Molecular Biology and Biotechnology, College of Life Sciences, Sichuan University, Chengdu 610064, China.
authors.forename: Yizheng
authors.initials: Y
authors.lastname: Zhang
authors.affiliation: Laboratory of Department of Surgery, the First Affiliated Hospital, Sun Yat-sen University, 58 Zhongshan Road II, Guangzhou, Guangdong 510080, China.
authors.forename: Wenjian
authors.initials: W
authors.lastname: Wang
authors.affiliation: Biomedical Research Centre, Norwich Medical School, University of East Anglia, Norwich Research Park, Norwich NR4 7TJ, UK.
authors.forename: Changjiang
authors.initials: C
authors.lastname: Dong
mesh_terms: D001425:Bacterial Outer Membrane Proteins / Q000737:chemistry* / Q000378:metabolism*; D018360:Crystallography, X-Ray; D004926:Escherichia coli / Q000737:chemistry*; D029968:Escherichia coli Proteins / Q000737:chemistry* / Q000378:metabolism*; D008074:Lipoproteins / Q000737:chemistry / Q000378:metabolism; D008958:Models, Molecular; D056004:Molecular Dynamics Simulation; D009068:Movement; D046912:Multiprotein Complexes / Q000737:chemistry* / Q000378:metabolism*; D019897:Periplasm / Q000378:metabolism; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D021122:Protein Subunits / Q000737:chemistry / Q000378:metabolism; D012399:Rotation
chemical_list: D001425:Bacterial Outer Membrane Proteins; C503914:BamA protein, E coli; D029968:Escherichia coli Proteins; D008074:Lipoproteins; D046912:Multiprotein Complexes; D021122:Protein Subunits