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  • 1
    Publication Date: 2010-11-12
    Description: Mononuclear iron-containing oxygenases conduct a diverse variety of oxidation functions in biology, including the oxidative demethylation of methylated nucleic acids and histones. Escherichia coli AlkB is the first such enzyme that was discovered to repair methylated nucleic acids, which are otherwise cytotoxic and/or mutagenic. AlkB human homologues are known to play pivotal roles in various processes. Here we present structural characterization of oxidation intermediates for these demethylases. Using a chemical cross-linking strategy, complexes of AlkB-double stranded DNA (dsDNA) containing 1,N(6)-etheno adenine (epsilonA), N(3)-methyl thymine (3-meT) and N(3)-methyl cytosine (3-meC) are stabilized and crystallized, respectively. Exposing these crystals, grown under anaerobic conditions containing iron(II) and alpha-ketoglutarate (alphaKG), to dioxygen initiates oxidation in crystallo. Glycol (from epsilonA) and hemiaminal (from 3-meT) intermediates are captured; a zwitterionic intermediate (from 3-meC) is also proposed, based on crystallographic observations and computational analysis. The observation of these unprecedented intermediates provides direct support for the oxidative demethylation mechanism for these demethylases. This study also depicts a general mechanistic view of how a methyl group is oxidatively removed from different biological substrates.〈br /〉〈br /〉〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3058853/" target="_blank"〉〈img src="https://static.pubmed.gov/portal/portal3rc.fcgi/4089621/img/3977009" border="0"〉〈/a〉   〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3058853/" target="_blank"〉This paper as free author manuscript - peer-reviewed and accepted for publication〈/a〉〈br /〉〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Yi, Chengqi -- Jia, Guifang -- Hou, Guanhua -- Dai, Qing -- Zhang, Wen -- Zheng, Guanqun -- Jian, Xing -- Yang, Cai-Guang -- Cui, Qiang -- He, Chuan -- GM071440/GM/NIGMS NIH HHS/ -- GM084028/GM/NIGMS NIH HHS/ -- R01 GM071440/GM/NIGMS NIH HHS/ -- R01 GM071440-06/GM/NIGMS NIH HHS/ -- England -- Nature. 2010 Nov 11;468(7321):330-3. doi: 10.1038/nature09497.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Chemistry and Institute for Biophysical Dynamics, The University of Chicago, 929 East 57th Street, Chicago, Illinois 60637, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/21068844" target="_blank"〉PubMed〈/a〉
    Keywords: Catalysis ; Cross-Linking Reagents/chemistry ; Crystallization ; Crystallography, X-Ray ; DNA/chemistry/metabolism ; *DNA Repair ; DNA Repair Enzymes/metabolism ; Dioxygenases/chemistry/*metabolism ; Escherichia coli/*enzymology ; Escherichia coli Proteins/chemistry/*metabolism ; Humans ; Iron/*metabolism ; Ketoglutaric Acids/metabolism ; Methylation ; Mixed Function Oxygenases/chemistry/*metabolism ; Models, Molecular ; Oxidation-Reduction ; Static Electricity ; Substrate Specificity
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
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  • 2
    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
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