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  • 1
    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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  • 2
    Publication Date: 2015-11-03
    Description: DNA methylation is an important epigenetic modification. Ten-eleven translocation (TET) proteins are involved in DNA demethylation through iteratively oxidizing 5-methylcytosine (5mC) into 5-hydroxymethylcytosine (5hmC), 5-formylcytosine (5fC) and 5-carboxylcytosine (5caC). Here we show that human TET1 and TET2 are more active on 5mC-DNA than 5hmC/5fC-DNA substrates. We determine the crystal structures of TET2-5hmC-DNA and TET2-5fC-DNA complexes at 1.80 A and 1.97 A resolution, respectively. The cytosine portion of 5hmC/5fC is specifically recognized by TET2 in a manner similar to that of 5mC in the TET2-5mC-DNA structure, and the pyrimidine base of 5mC/5hmC/5fC adopts an almost identical conformation within the catalytic cavity. However, the hydroxyl group of 5hmC and carbonyl group of 5fC face towards the opposite direction because the hydroxymethyl group of 5hmC and formyl group of 5fC adopt restrained conformations through forming hydrogen bonds with the 1-carboxylate of NOG and N4 exocyclic nitrogen of cytosine, respectively. Biochemical analyses indicate that the substrate preference of TET2 results from the different efficiencies of hydrogen abstraction in TET2-mediated oxidation. The restrained conformation of 5hmC and 5fC within the catalytic cavity may prevent their abstractable hydrogen(s) adopting a favourable orientation for hydrogen abstraction and thus result in low catalytic efficiency. Our studies demonstrate that the substrate preference of TET2 results from the intrinsic value of its substrates at their 5mC derivative groups and suggest that 5hmC is relatively stable and less prone to further oxidation by TET proteins. Therefore, TET proteins are evolutionarily tuned to be less reactive towards 5hmC and facilitate the generation of 5hmC as a potentially stable mark for regulatory functions.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Hu, Lulu -- Lu, Junyan -- Cheng, Jingdong -- Rao, Qinhui -- Li, Ze -- Hou, Haifeng -- Lou, Zhiyong -- Zhang, Lei -- Li, Wei -- Gong, Wei -- Liu, Mengjie -- Sun, Chang -- Yin, Xiaotong -- Li, Jie -- Tan, Xiangshi -- Wang, Pengcheng -- Wang, Yinsheng -- Fang, Dong -- Cui, Qiang -- Yang, Pengyuan -- He, Chuan -- Jiang, Hualiang -- Luo, Cheng -- Xu, Yanhui -- Howard Hughes Medical Institute/ -- England -- Nature. 2015 Nov 5;527(7576):118-22. doi: 10.1038/nature15713. Epub 2015 Oct 28.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Fudan University Shanghai Cancer Center, Institute of Biomedical Sciences, Shanghai Medical College of Fudan University, Shanghai 200032, China. ; Key Laboratory of Molecular Medicine, Ministry of Education, Department of Systems Biology for Medicine, School of Basic Medical Sciences, Shanghai Medical College of Fudan University, Shanghai 200032, China. ; State Key Laboratory of Genetic Engineering, Collaborative Innovation Center of Genetics and Development, School of Life Sciences, Fudan University, Shanghai 200433, China. ; Drug Discovery and Design Center, State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai 201203, China. ; Beijing Synchrotron Radiation Facility, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049, China. ; Laboratory of Structural Biology, Tsinghua University, Beijing 100084, China. ; MOE Laboratory of Protein Science, School of Medicine, Tsinghua University, Beijing 100084, China. ; Department of Chemistry, University of California-Riverside, Riverside, California 92521-0403, USA. ; Theoretical Chemistry Institute, Department of Chemistry, University of Wisconsin-Madison, 1101 University Avenue, Madison, Wisconsin 53706, USA. ; Department of Chemistry and Institute for Biophysical Dynamics, The University of Chicago, 929 East 57th Street, Chicago, Illinois 60637, USA. ; Howard Hughes Medical Institute, 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/26524525" target="_blank"〉PubMed〈/a〉
    Keywords: 5-Methylcytosine/metabolism ; Biocatalysis ; Catalytic Domain ; Crystallography, X-Ray ; Cytosine/analogs & derivatives/metabolism ; DNA/*chemistry/*metabolism ; DNA Methylation ; DNA-Binding Proteins/*chemistry/*metabolism ; Humans ; Hydrogen Bonding ; Models, Molecular ; Oxidation-Reduction ; Protein Binding ; Proto-Oncogene Proteins/*chemistry/*metabolism ; Substrate Specificity
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    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
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  • 3
    Publication Date: 2015-07-01
    Description: DNA methylation at selective cytosine residues (5-methylcytosine (5mC)) and their removal by TET-mediated DNA demethylation are critical for setting up pluripotent states in early embryonic development. TET enzymes successively convert 5mC to 5-hydroxymethylcytosine (5hmC), 5-formylcytosine (5fC), and 5-carboxylcytosine (5caC), with 5fC and 5caC subject to removal by thymine DNA glycosylase (TDG) in conjunction with base excision repair. Early reports indicate that 5fC and 5caC could be stably detected on enhancers, promoters and gene bodies, with distinct effects on gene expression, but the mechanisms have remained elusive. Here we determined the X-ray crystal structure of yeast elongating RNA polymerase II (Pol II) in complex with a DNA template containing oxidized 5mCs, revealing specific hydrogen bonds between the 5-carboxyl group of 5caC and the conserved epi-DNA recognition loop in the polymerase. This causes a positional shift for incoming nucleoside 5'-triphosphate (NTP), thus compromising nucleotide addition. To test the implication of this structural insight in vivo, we determined the global effect of increased 5fC/5caC levels on transcription, finding that such DNA modifications indeed retarded Pol II elongation on gene bodies. These results demonstrate the functional impact of oxidized 5mCs on gene expression and suggest a novel role for Pol II as a specific and direct epigenetic sensor during transcription elongation.〈br /〉〈br /〉〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4521995/" 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/PMC4521995/" target="_blank"〉This paper as free author manuscript - peer-reviewed and accepted for publication〈/a〉〈br /〉〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Wang, Lanfeng -- Zhou, Yu -- Xu, Liang -- Xiao, Rui -- Lu, Xingyu -- Chen, Liang -- Chong, Jenny -- Li, Hairi -- He, Chuan -- Fu, Xiang-Dong -- Wang, Dong -- GM052872/GM/NIGMS NIH HHS/ -- GM102362/GM/NIGMS NIH HHS/ -- HG004659/HG/NHGRI NIH HHS/ -- HG006827/HG/NHGRI NIH HHS/ -- R01 GM052872/GM/NIGMS NIH HHS/ -- R01 GM102362/GM/NIGMS NIH HHS/ -- R01 HG004659/HG/NHGRI NIH HHS/ -- R01 HG006827/HG/NHGRI NIH HHS/ -- Howard Hughes Medical Institute/ -- England -- Nature. 2015 Jul 30;523(7562):621-5. doi: 10.1038/nature14482. Epub 2015 Jun 29.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Skaggs School of Pharmacy and Pharmaceutical Sciences, The University of California, San Diego, 9500 Gilman Drive, La Jolla, California 92093, USA. ; Department of Cellular and Molecular Medicine, School of Medicine, The University of California, San Diego, 9500 Gilman Drive, La Jolla, California 92093, USA. ; Department of Chemistry, Department of Biochemistry and Molecular Biology, and Institute for Biophysical Dynamics, Howard Hughes Medical Institute, The University of Chicago, Chicago, Illinois 60637, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/26123024" target="_blank"〉PubMed〈/a〉
    Keywords: Crystallography, X-Ray ; Cytosine/*analogs & derivatives/chemistry/metabolism ; DNA Methylation ; DNA Repair ; Epigenesis, Genetic ; Hydrogen Bonding ; Kinetics ; RNA Polymerase II/*chemistry/*metabolism ; Saccharomyces cerevisiae/*enzymology/genetics/metabolism ; Substrate Specificity ; Templates, Genetic ; Thymine DNA Glycosylase/metabolism ; *Transcription Elongation, Genetic
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    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
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  • 4
    Publication Date: 2008-04-25
    Description: Escherichia coli AlkB and its human homologues ABH2 and ABH3 repair DNA/RNA base lesions by using a direct oxidative dealkylation mechanism. ABH2 has the primary role of guarding mammalian genomes against 1-meA damage by repairing this lesion in double-stranded DNA (dsDNA), whereas AlkB and ABH3 preferentially repair single-stranded DNA (ssDNA) lesions and can repair damaged bases in RNA. Here we show the first crystal structures of AlkB-dsDNA and ABH2-dsDNA complexes, stabilized by a chemical cross-linking strategy. This study reveals that AlkB uses an unprecedented base-flipping mechanism to access the damaged base: it squeezes together the two bases flanking the flipped-out one to maintain the base stack, explaining the preference of AlkB for repairing ssDNA lesions over dsDNA ones. In addition, the first crystal structure of ABH2, presented here, provides a structural basis for designing inhibitors of this human DNA repair protein.〈br /〉〈br /〉〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2587245/" 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/PMC2587245/" target="_blank"〉This paper as free author manuscript - peer-reviewed and accepted for publication〈/a〉〈br /〉〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Yang, Cai-Guang -- Yi, Chengqi -- Duguid, Erica M -- Sullivan, Christopher T -- Jian, Xing -- Rice, Phoebe A -- He, Chuan -- GM071440/GM/NIGMS NIH HHS/ -- R01 GM071440/GM/NIGMS NIH HHS/ -- R01 GM071440-03/GM/NIGMS NIH HHS/ -- England -- Nature. 2008 Apr 24;452(7190):961-5. doi: 10.1038/nature06889.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Chemistry, 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/18432238" target="_blank"〉PubMed〈/a〉
    Keywords: Adenine/analogs & derivatives/metabolism ; Binding Sites ; Cross-Linking Reagents/chemistry ; Crystallography, X-Ray ; DNA/chemistry/*metabolism ; DNA Damage ; DNA Repair ; DNA Repair Enzymes/*chemistry/metabolism ; DNA-Binding Proteins/chemistry/metabolism ; Dioxygenases/*chemistry/*metabolism ; Escherichia coli Proteins/*chemistry/*metabolism ; Humans ; Mixed Function Oxygenases/*chemistry/*metabolism ; Models, Molecular ; Protein Binding ; RNA/*metabolism
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
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  • 5
    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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