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  • 1
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    Structural basis for outer membrane lipopolysaccharide insertion (2014)
    Nature Publishing Group (NPG)
    Details
    Publication Date: 2014-07-06
    Description: Lipopolysaccharide (LPS) is essential for most Gram-negative bacteria and has crucial roles in protection of the bacteria from harsh environments and toxic compounds, including antibiotics. Seven LPS transport proteins (that is, LptA-LptG) form a trans-envelope protein complex responsible for the transport of LPS from the inner membrane to the outer membrane, the mechanism for which is poorly understood. Here we report the first crystal structure of the unique integral membrane LPS translocon LptD-LptE complex. LptD forms a novel 26-stranded beta-barrel, which is to our knowledge the largest beta-barrel reported so far. LptE adopts a roll-like structure located inside the barrel of LptD to form an unprecedented two-protein 'barrel and plug' architecture. The structure, molecular dynamics simulations and functional assays suggest that the hydrophilic O-antigen and the core oligosaccharide of the LPS may pass through the barrel and the lipid A of the LPS may be inserted into the outer leaflet of the outer membrane through a lateral opening between strands beta1 and beta26 of LptD. These findings not only help us to understand important aspects of bacterial outer membrane biogenesis, but also have significant potential for the development of novel drugs against multi-drug resistant pathogenic bacteria.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Dong, Haohao -- Xiang, Quanju -- Gu, Yinghong -- Wang, Zhongshan -- Paterson, Neil G -- Stansfeld, Phillip J -- He, Chuan -- Zhang, Yizheng -- Wang, Wenjian -- Dong, Changjiang -- 083501/Z/07/Z/Wellcome Trust/United Kingdom -- England -- Nature. 2014 Jul 3;511(7507):52-6. doi: 10.1038/nature13464. Epub 2014 Jun 18.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉1] Biomedical Research Centre, Norwich Medical School, University of East Anglia, Norwich Research Park, Norwich NR4 7TJ, UK [2] Biomedical Sciences Research Complex, School of Chemistry, University of St Andrews, North Haugh, St Andrews KY16 9ST, UK. ; 1] Biomedical Sciences Research Complex, School of Chemistry, University of St Andrews, North Haugh, St Andrews KY16 9ST, UK [2] Department of Microbiology, College of Resource and Environment Science, Sichuan Agriculture University, Yaan 625000, China. ; Biomedical Research Centre, Norwich Medical School, University of East Anglia, Norwich Research Park, Norwich NR4 7TJ, UK. ; 1] Biomedical Research Centre, Norwich Medical School, University of East Anglia, Norwich Research Park, Norwich NR4 7TJ, UK [2] Biomedical Sciences Research Complex, School of Chemistry, University of St Andrews, North Haugh, St Andrews KY16 9ST, UK [3] College of Life Sciences, Sichuan University, Chengdu 610065, China. ; Diamond Light Source, Harwell Science and Innovation Campus, Didcot OX11 0DE, UK. ; Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, UK. ; 1] Biomedical Sciences Research Complex, School of Chemistry, University of St Andrews, North Haugh, St Andrews KY16 9ST, UK [2] School of Electronics and Information, Wuhan Technical College of Communications, No.6 Huangjiahu West Road, Hongshan District, Wuhan, Hubei 430065, China. ; College of Life Sciences, Sichuan University, Chengdu 610065, China. ; Laboratory of Department of Surgery, the First Affiliated Hospital, Sun Yat-sen University, 58 Zhongshan Road II, Guangzhou, Guangdong 510080, China.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/24990744" target="_blank"〉PubMed〈/a〉
    Keywords: Bacterial Outer Membrane Proteins/*chemistry/*metabolism ; Cell Membrane/chemistry/metabolism ; Cell Wall/chemistry/metabolism ; Crystallography, X-Ray ; Lipopolysaccharides/chemistry/*metabolism ; Models, Molecular ; Multiprotein Complexes/*chemistry/*metabolism ; Protein Binding ; Protein Structure, Secondary ; Salmonella typhimurium/*chemistry/cytology ; Structure-Activity Relationship
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Published by Nature Publishing Group (NPG)
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  • 2
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    Structural basis of outer membrane protein insertion by the BAM complex (2016)
    Nature Publishing Group (NPG)
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    Publication Date: 2016-02-24
    Description: 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 beta-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 beta-barrel of BamA to induce movement of the beta-strands of the barrel and promote insertion of the nascent OMP.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Gu, Yinghong -- Li, Huanyu -- Dong, Haohao -- Zeng, Yi -- Zhang, Zhengyu -- Paterson, Neil G -- Stansfeld, Phillip J -- Wang, Zhongshan -- Zhang, Yizheng -- Wang, Wenjian -- Dong, Changjiang -- G1100110/1/Medical Research Council/United Kingdom -- WT106121MA/Wellcome Trust/United Kingdom -- England -- Nature. 2016 Mar 3;531(7592):64-9. doi: 10.1038/nature17199. Epub 2016 Feb 22.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Biomedical Research Centre, Norwich Medical School, University of East Anglia, Norwich Research Park, Norwich NR4 7TJ, UK. ; Diamond Light Source, Harwell Science and Innovation Campus, Didcot, Oxfordshire OX11 0DE, UK. ; Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, 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. ; Laboratory of Department of Surgery, the First Affiliated Hospital, Sun Yat-sen University, 58 Zhongshan Road II, Guangzhou, Guangdong 510080, China.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/26901871" target="_blank"〉PubMed〈/a〉
    Keywords: Bacterial Outer Membrane Proteins/*chemistry/*metabolism ; Crystallography, X-Ray ; Escherichia coli/*chemistry ; Escherichia coli Proteins/*chemistry/*metabolism ; Lipoproteins/chemistry/metabolism ; Models, Molecular ; Molecular Dynamics Simulation ; Movement ; Multiprotein Complexes/*chemistry/*metabolism ; Periplasm/metabolism ; Protein Binding ; Protein Structure, Tertiary ; Protein Subunits/chemistry/metabolism ; Rotation
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Published by Nature Publishing Group (NPG)
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  • 3
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    An approach to space power (1990)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: Fusion offers the potential for a very high specific power, providing a large specific impulse that can be traded-off with thrust for mission optimization. Thus fusion is a leading candidate for missions beyond the moon. A new approach is discussed for space fusion power, namely Inertial Electrostatic Confinement (IEC). This method offers a high power density in a relatively small, simple device. It appears capable of burning aneutronic fuels which are most desirable for space applications and is well suited for direct conversion. An experimental device to test the concept is described.
    Keywords: SPACECRAFT PROPULSION AND POWER
    Type: NASA. Lewis Research Center, Vision-21: Space Travel for the Next Millennium; p 141-149
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  • 4
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    Inertial electrostatic confinement as a power source for electric propulsion (1993)
    In:  CASI
    Details
    Publication Date: 2019-08-27
    Description: The potential use of an Inertial Electrostatic Confinement (IEC) power source for space propulsion has previously been suggested by the authors and others. In the past, these discussions have generally followed the charged-particle electric-discharge engine (QED) concept proposed by Bussard, in which the IEC is used to generate an electron beam which vaporizes liquid hydrogen for use as a propellant. However, in the present study, we consider an alternate approach, using the IEC to drive a conventional electric thruster unit. This has the advantage of building on the rapidly developing technology for such thrusters, which operate at higher specific impulse. Key issues related to this approach include the continued successful development of the physics and engineering of the IEC unit, as well as the development of efficient step-down dc voltage transformers. The IEC operates by radial injection of energetic ions into a spherical vessel. A very high ion density is created in a small core region at the center of the vessel, resulting in extremely high fusion power density in the core. Present experiments at the U. of Illinois in small IEC devices (less than 60-cm. dia.) have demonstrated much of the basic physics underlying this concept, e.g. producing approximately 10(exp 6) D-D neutrons/sec steady-state with deuterium gas flow injection. The ultimate goal is to increase the power densities by several orders of magnitude and to convert to D-He-3 injection. If successful, such an experiment would represent a milestone proof-of-principle device for eventual space power use. Further discussion of IEC physics and status will be presented with a description of the overall propulsion system and estimated performance.
    Keywords: SPACECRAFT PROPULSION AND POWER
    Type: NASA. Lewis Research Center, Vision 21: Interdisciplinary Science and Engineering in the Era of Cyberspace; p 185-229
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  • 5
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    Inertial electrostatic confinement as a power source for electric propulsion (1993)
    In:  CASI
    Details
    Publication Date: 2019-08-28
    Description: The potential use of an INERTIAL ELECTROSTATIC CONFINEMENT (IEC) power source for space propulsion has previously been suggested by the authors and others. In the past, these discussions have generally followed the charged-particle electric-discharge engine (QED) concept proposed by Bussard, in which the IEC is used to generate an electron beam which vaporizes liquid hydrogen for use as a propellant. However, an alternate approach is considered, using the IEC to drive a 'conventional' electric thruster unit. This has the advantage of building on the rapidly developing technology for such thrusters, which operate at higher specific impulse. Key issues related to this approach include the continued successful development of the physics and engineering of the IEC unit, as well as the development of efficient step-down dc voltage transformers. The IEC operates by radial injection of energetic ions into a spherical vessel. A very high ion density is created in a small core region at the center of the vessel, resulting in extremely high fusion power density in the core. Experiments at the U. of Illinois in small IEC devices (is less than 60 cm. dia.) demonstrated much of the basic physics underlying this concept, e.g. producing 10(exp 6) D-D neutrons/sec steady-state with deuterium gas flow injection. The ultimate goal is to increase the power densities by several orders of magnitude and to convert to D-He-3 injection. If successful, such an experiment would represent a milestone proof-of-principle device for eventual space power use. Further discussion of IEC physics and status are presented with a description of the overall propulsion system and estimated performance.
    Keywords: SPACECRAFT PROPULSION AND POWER
    Type: NASA-TM-109228 , NAS 1.15:109228 , FSL-422 , Vision 21 Conference; Mar 30, 1993 - Mar 31, 1993; Cleveland, OH; United States
    Format: application/pdf
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