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  • 1
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    A model for the mechanism of human topoisomerase I (1998)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1998-03-21
    Description: The three-dimensional structure of a 70-kilodalton amino terminally truncated form of human topoisomerase I in complex with a 22-base pair duplex oligonucleotide, determined to a resolution of 2.8 angstroms, reveals all of the structural elements of the enzyme that contact DNA. The linker region that connects the central core of the enzyme to the carboxyl-terminal domain assumes a coiled-coil configuration and protrudes away from the remainder of the enzyme. The positively charged DNA-proximal surface of the linker makes only a few contacts with the DNA downstream of the cleavage site. In combination with the crystal structures of the reconstituted human topoisomerase I before and after DNA cleavage, this information suggests which amino acid residues are involved in catalyzing phosphodiester bond breakage and religation. The structures also lead to the proposal that the topoisomerization step occurs by a mechanism termed "controlled rotation."〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Stewart, L -- Redinbo, M R -- Qiu, X -- Hol, W G -- Champoux, J J -- CA65656/CA/NCI NIH HHS/ -- GM16713/GM/NIGMS NIH HHS/ -- GM49156/GM/NIGMS NIH HHS/ -- New York, N.Y. -- Science. 1998 Mar 6;279(5356):1534-41.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Biomolecular Structure Center and Department of Biological Structure, School of Medicine, University of Washington, Seattle, WA 98195-7742, USA. emerald_biostructures@rocketmail.com〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9488652" target="_blank"〉PubMed〈/a〉
    Keywords: Amino Acid Sequence ; Arginine/chemistry/metabolism ; Binding Sites ; Catalysis ; Crystallography, X-Ray ; DNA/chemistry/*metabolism ; DNA Topoisomerases, Type I/*chemistry/*metabolism ; Humans ; Hydrogen Bonding ; *Models, Chemical ; Models, Molecular ; Molecular Sequence Data ; Nucleic Acid Conformation ; Oligodeoxyribonucleotides/chemistry/metabolism ; *Protein Conformation ; Protein Structure, Secondary ; Tyrosine/chemistry/metabolism
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 2
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    Structure of the VHL-ElonginC-ElonginB complex: implications for VHL tumor suppressor function (1999)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1999-04-16
    Description: Mutation of the VHL tumor suppressor is associated with the inherited von Hippel-Lindau (VHL) cancer syndrome and the majority of kidney cancers. VHL binds the ElonginC-ElonginB complex and regulates levels of hypoxia-inducible proteins. The structure of the ternary complex at 2.7 angstrom resolution shows two interfaces, one between VHL and ElonginC and another between ElonginC and ElonginB. Tumorigenic mutations frequently occur in a 35-residue domain of VHL responsible for ElonginC binding. A mutational patch on a separate domain of VHL indicates a second macromolecular binding site. The structure extends the similarities to the SCF (Skp1-Cul1-F-box protein) complex that targets proteins for degradation, supporting the hypothesis that VHL may function in an analogous pathway.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Stebbins, C E -- Kaelin, W G Jr -- Pavletich, N P -- New York, N.Y. -- Science. 1999 Apr 16;284(5413):455-61.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Biochemistry and Structural Biology, Joan and Sanford I. Weill Graduate School of Medical Sciences, Cornell University, New York, NY 10021, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/10205047" target="_blank"〉PubMed〈/a〉
    Keywords: Amino Acid Sequence ; Binding Sites ; Cell Cycle Proteins/chemistry/metabolism ; Cloning, Molecular ; Crystallography, X-Ray ; *Genes, Tumor Suppressor ; Humans ; Hydrogen Bonding ; *Ligases ; Models, Molecular ; Molecular Sequence Data ; Mutation ; Mutation, Missense ; Neoplasms/genetics ; Protein Conformation ; Protein Folding ; Protein Structure, Secondary ; Proteins/*chemistry/genetics/metabolism ; S-Phase Kinase-Associated Proteins ; Surface Properties ; Transcription Factors/*chemistry/metabolism ; *Tumor Suppressor Proteins ; *Ubiquitin-Protein Ligases ; Von Hippel-Lindau Tumor Suppressor Protein ; von Hippel-Lindau Disease/*genetics
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 3
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    Inhibition of the hammerhead ribozyme cleavage reaction by site-specific binding of Tb (1998)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1998-01-24
    Description: Terbium(III) [Tb(III)] was shown to inhibit the hammerhead ribozyme by competing with a single magnesium(II) ion. X-ray crystallography revealed that the Tb(III) ion binds to a site adjacent to an essential guanosine in the catalytic core of the ribozyme, approximately 10 angstroms from the cleavage site. Synthetic modifications near this binding site yielded an RNA substrate that was resistant to Tb(III) binding and capable of being cleaved, even in the presence of up to 20 micromolar Tb(III). It is suggested that the magnesium(II) ion thought to bind at this site may act as a switch, affecting the conformational changes required to achieve the transition state.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Feig, A L -- Scott, W G -- Uhlenbeck, O C -- GM-36944/GM/NIGMS NIH HHS/ -- New York, N.Y. -- Science. 1998 Jan 2;279(5347):81-4.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Chemistry and Biochemistry, University of Colorado, Boulder, CO 80309, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9417029" target="_blank"〉PubMed〈/a〉
    Keywords: Binding Sites ; Binding, Competitive ; Catalysis ; Crystallography, X-Ray ; Magnesium/metabolism ; Models, Molecular ; Nucleic Acid Conformation ; RNA, Catalytic/*antagonists & inhibitors/chemistry/*metabolism ; Terbium/*metabolism/pharmacology
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 4
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    Crystal structures of human topoisomerase I in covalent and noncovalent complexes with DNA (1998)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1998-03-21
    Description: Topoisomerases I promote the relaxation of DNA superhelical tension by introducing a transient single-stranded break in duplex DNA and are vital for the processes of replication, transcription, and recombination. The crystal structures at 2.1 and 2.5 angstrom resolution of reconstituted human topoisomerase I comprising the core and carboxyl-terminal domains in covalent and noncovalent complexes with 22-base pair DNA duplexes reveal an enzyme that "clamps" around essentially B-form DNA. The core domain and the first eight residues of the carboxyl-terminal domain of the enzyme, including the active-site nucleophile tyrosine-723, share significant structural similarity with the bacteriophage family of DNA integrases. A binding mode for the anticancer drug camptothecin is proposed on the basis of chemical and biochemical information combined with these three-dimensional structures of topoisomerase I-DNA complexes.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Redinbo, M R -- Stewart, L -- Kuhn, P -- Champoux, J J -- Hol, W G -- CA65656/CA/NCI NIH HHS/ -- GM49156/GM/NIGMS NIH HHS/ -- New York, N.Y. -- Science. 1998 Mar 6;279(5356):1504-13.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Biomolecular Structure Center and Department of Biological Structure, Box 357742, School of Medicine, University of Washington, Seattle, WA 98195, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9488644" target="_blank"〉PubMed〈/a〉
    Keywords: Antineoplastic Agents, Phytogenic/metabolism/pharmacology ; Binding Sites ; Camptothecin/analogs & derivatives/metabolism/pharmacology ; Crystallography, X-Ray ; DNA/chemistry/*metabolism ; DNA Topoisomerases, Type I/*chemistry/genetics/metabolism ; *DNA-Binding Proteins ; Homeodomain Proteins/chemistry ; Host Cell Factor C1 ; Humans ; Hydrogen Bonding ; Integrases/chemistry ; Models, Molecular ; Mutation ; Nucleic Acid Conformation ; Octamer Transcription Factor-1 ; Oligodeoxyribonucleotides/chemistry/metabolism ; *Protein Conformation ; Protein Structure, Secondary ; Recombinant Proteins/chemistry ; Transcription Factors/chemistry ; Tyrosine/chemistry/metabolism
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 5
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    Mutagenesis and Laue structures of enzyme intermediates: isocitrate dehydrogenase (1995)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1995-06-02
    Description: Site-directed mutagenesis and Laue diffraction data to 2.5 A resolution were used to solve the structures of two sequential intermediates formed during the catalytic actions of isocitrate dehydrogenase. Both intermediates are distinct from the enzyme-substrate and enzyme-product complexes. Mutation of key catalytic residues changed the rate determining steps so that protein and substrate intermediates within the overall reaction pathway could be visualized.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Bolduc, J M -- Dyer, D H -- Scott, W G -- Singer, P -- Sweet, R M -- Koshland, D E Jr -- Stoddard, B L -- GM49857/GM/NIGMS NIH HHS/ -- New York, N.Y. -- Science. 1995 Jun 2;268(5215):1312-8.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Fred Hutchinson Cancer Research Center, Program in Structural Biology, Seattle, WA 98104, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/7761851" target="_blank"〉PubMed〈/a〉
    Keywords: Binding Sites ; Catalysis ; Computer Graphics ; *Crystallography, X-Ray ; Isocitrate Dehydrogenase/*chemistry/genetics/metabolism ; Isocitrates/metabolism ; Kinetics ; *Mutagenesis, Site-Directed ; NADP/metabolism ; Protein Conformation
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 6
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    A functionally diverse enzyme superfamily that abstracts the alpha protons of carboxylic acids (1995)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1995-02-24
    Description: Mandelate racemase and muconate lactonizing enzyme are structurally homologous but catalyze different reactions, each initiated by proton abstraction from carbon. The structural similarity to mandelate racemase of a previously unidentified gene product was used to deduce its function as a galactonate dehydratase. In this enzyme superfamily that has evolved to catalyze proton abstraction from carbon, three variations of homologous active site architectures are now represented: lysine and histidine bases in the active site of mandelate racemase, only a lysine base in the active site of muconate lactonizing enzyme, and only a histidine base in the active site of galactonate dehydratase. This discovery supports the hypothesis that new enzymatic activities evolve by recruitment of a protein catalyzing the same type of chemical reaction.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Babbitt, P C -- Mrachko, G T -- Hasson, M S -- Huisman, G W -- Kolter, R -- Ringe, D -- Petsko, G A -- Kenyon, G L -- Gerlt, J A -- GM-34572/GM/NIGMS NIH HHS/ -- GM-40570/GM/NIGMS NIH HHS/ -- New York, N.Y. -- Science. 1995 Feb 24;267(5201):1159-61.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Pharmaceutical Chemistry, School of Pharmacy, University of California, San Francisco 94143.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/7855594" target="_blank"〉PubMed〈/a〉
    Keywords: Amino Acid Sequence ; Base Sequence ; Binding Sites ; Histidine/metabolism ; Hydro-Lyases/chemistry/genetics/*metabolism ; *Intramolecular Lyases ; Isomerases/chemistry/*metabolism ; Lysine/metabolism ; Molecular Sequence Data ; Open Reading Frames ; Operon ; *Protons ; Pseudomonas putida/*enzymology/genetics ; Racemases and Epimerases/chemistry/*metabolism
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 7
    Electronic Resource
    Electronic Resource
    Extent of chiral inversion of the 2-arylpropionic acids by Cordyceps militaris (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 10 (1998), S. 528-534 
    Details
    ISSN: 0899-0042
    Keywords: chiral inversion ; ibuprofen ; ketoprofen ; flurbiprofen ; indoprofen ; suprofen ; fenoprofen ; metabolism of 2-arylpropionic acids ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The fungus Cordyceps militaris has been previously shown to be capable of inverting the chirality of 2-phenylpropionic acid from its (R)-enantiomer to its (S)-antipode. The structure of this compound is similar to the 2-arylpropionic acid non-steroidal anti-inflammatory drugs, which have also been reported to undergo a similar chiral inversion process in mammals and man. We report here an investigation into the substrate specificity of the enzyme system present in C. militaris using pure enantiomers and racemates of ibuprofen and ketoprofen and racemates of indoprofen, suprofen, flurbiprofen, and fenoprofen and the structurally related compounds 2-phenylbutyric acid and 2-phenoxypropionic acid as substrates, using optimised incubation conditions developed for the inversion of 2-phenylpropionic acid. The results demonstrated that C. militaris is capable of inverting the chirality of all the compounds investigated, which suggests that the active sites of the enzymes are very flexible with regard to the molecular dimensions of the substrate molecule and the spatial occupation of the groups surrounding the chiral centre. Metabolism of all the substrates was observed but the rate of metabolism varied extensively depending on the substrate. Achiral HPLC analysis was used to detect any potential metabolites and the results suggested that the site of the metabolism appeared to be at the aliphatic side groups only, with the aromatic ring being left intact in all cases. These results suggest that C. militaris could be a valuable tool in the investigation of the prospective metabolic fates of new 2-arylpropionic acids during their development. Chirality 10:528-534, 1998. © 1998 Wiley-Liss, Inc.
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  • 8
    Electronic Resource
    Electronic Resource
    A mechanistic investigation of the microbial chiral inversion of 2-phenylpropionic acid by Verticillium lecanii (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 9 (1997), S. 254-260 
    Details
    ISSN: 0899-0042
    Keywords: microbial chiral inversion ; 2-phenylpropionic acid ; kinetic isotope effect ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Previous investigations have described the development of nongrowing suspension of Verticillium lecanii as a microbial model of the mammalian chiral inversion of the 2-arylpropionic acids (2-APAs). Mechanistic studies in mammals have shown that inversion involves loss of the α-methine proton but retention of the original atoms at the β-methyl position, and a mechanism has been proposed involving enzymatic epimerisation of acyl-CoA thioester derivatives of the substrate. Inversion of the 2-APAs by V. lecanii exhibits extensive intersubstrate variation in the presence, rate, extent, and direction of inversion, which are different from those observed in mammalian systems, possibly indicating differences in the mechanism of inversion between mammalian and microbial cells. This study involved the investigation of proton/deuterium exchange by 1H-nuclear magnetic resonance following incubation of deuterated derivatives of 2-phenylpropionic acid (2-PPA), a model compound, in cell suspensions of V. lecanii and incubation of undeuterated 2-PPA in cell suspensions containing D2O. The results indicated that the inversion of 2-PPA by V. lecanii also involved exchange of the α-methine proton but complete retention on the original atoms at the β-methyl position. No kinetic deuterium isotope effect was observed, indicating that loss of the α-methine proton is not the rate-limiting step of the inversion process. This suggests that the observed differences between microbial and mammalian systems probably involve the stereoselective acyl-CoA thioester formation step and not the subsequent epimerisation of the resultant diastereomers. Chirality 9:254-260, 1997. © 1997 Wiley-Liss, Inc.
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