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  • Kinetics  (25)
  • American Association for the Advancement of Science (AAAS)  (25)
  • 2005-2009  (6)
  • 1985-1989  (19)
  • 1980-1984
  • 2006  (6)
  • 1988  (19)
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Publisher
  • American Association for the Advancement of Science (AAAS)  (25)
  • Springer  (1)
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  • 2005-2009  (6)
  • 1985-1989  (19)
  • 1980-1984
Year
  • 1
    Publication Date: 2006-09-16
    Description: We used nuclear magnetic resonance relaxation dispersion to characterize higher energy conformational substates of Escherichia coli dihydrofolate reductase. Each intermediate in the catalytic cycle samples low-lying excited states whose conformations resemble the ground-state structures of preceding and following intermediates. Substrate and cofactor exchange occurs through these excited substates. The maximum hydride transfer and steady-state turnover rates are governed by the dynamics of transitions between ground and excited states of the intermediates. Thus, the modulation of the energy landscape by the bound ligands funnels the enzyme through its reaction cycle along a preferred kinetic path.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Boehr, David D -- McElheny, Dan -- Dyson, H Jane -- Wright, Peter E -- GM56879/GM/NIGMS NIH HHS/ -- GM75995/GM/NIGMS NIH HHS/ -- New York, N.Y. -- Science. 2006 Sep 15;313(5793):1638-42.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Molecular Biology and Skaggs Institute for Chemical Biology, Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, CA 92037, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/16973882" target="_blank"〉PubMed〈/a〉
    Keywords: Binding Sites ; Catalysis ; Escherichia coli/*enzymology ; Kinetics ; Ligands ; Models, Molecular ; NADP/metabolism ; Nuclear Magnetic Resonance, Biomolecular ; Protein Binding ; *Protein Conformation ; Tetrahydrofolate Dehydrogenase/*chemistry/*metabolism ; Tetrahydrofolates/metabolism ; Thermodynamics
    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
    Publication Date: 1988-09-02
    Description: Catalysis of amide bond hydrolysis is of singular importance in enzymology. An antibody was induced to an analog of a high-energy intermediate anticipated along the reaction coordinate of amide hydrolysis. This antibody is an amidase with high specificity and a large rate enhancement (250,000) relative to the uncatalyzed reaction. This reaction represents the kinetically most difficult hydrolysis reaction yet catalyzed by an antibody.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Janda, K D -- Schloeder, D -- Benkovic, S J -- Lerner, R A -- New York, N.Y. -- Science. 1988 Sep 2;241(4870):1188-91.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Molecular Biology, Research Institute of Scripps Clinic, La Jolla, CA 92037.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/3413482" target="_blank"〉PubMed〈/a〉
    Keywords: Amidohydrolases/metabolism ; Animals ; Antibodies, Monoclonal/biosynthesis/*physiology ; Antibody Specificity ; Antigens/immunology ; *Catalysis ; Chemical Phenomena ; Chemistry ; Hemocyanin/analogs & derivatives/immunology ; Hydrolysis ; Immunization ; Kinetics ; Mice ; Organophosphorus Compounds/immunology ; Substrate Specificity
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    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 3
    Publication Date: 1988-04-22
    Description: The three-dimensional structure of most enzymes is unknown; however, many enzymes may have structural motifs similar to those in the known structures of functionally related enzymes. Evidence is presented that an enzyme of unknown structure [Ile-transfer RNA (tRNA) synthetase] may share a functionally important structural motif with an enzyme of related function (Tyr-tRNA synthetase). This approach involves (i) identifying segments of Ile-tRNA synthetase that have been unusually conserved during evolution, (ii) predicting the function of one such segment by assuming a structural relation between Ile-tRNA synthetase and Tyr-tRNA synthetase, and (iii) testing the predicted function by mutagenesis and subsequent biochemical analysis. Random mutations were introduced by cassette mutagenesis into a ten-amino-acid segment of Ile-tRNA synthetase that was predicted to be involved in the formation of the binding site for isoleucine. Few amino acid substitutions appear to be tolerated in this region. However, one substitution (independently isolated twice) increased the Michaelis constant Km for isoleucine in the adenylate synthesis reaction by greater than 6000-fold, but had little effect on the Km for adenosine triphosphate, the apparent Km for tRNA, or the rate constant kcat.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Clarke, N D -- Lien, D C -- Schimmel, P -- GM15539/GM/NIGMS NIH HHS/ -- New York, N.Y. -- Science. 1988 Apr 22;240(4851):521-3.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Biology, Massachusetts Institute of Technology, Cambridge 02139.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/3282306" target="_blank"〉PubMed〈/a〉
    Keywords: *Amino Acyl-tRNA Synthetases ; Binding Sites ; DNA Mutational Analysis ; Escherichia coli/enzymology ; *Isoleucine-tRNA Ligase ; Kinetics ; Protein Conformation ; Saccharomyces cerevisiae/enzymology ; Structure-Activity Relationship
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  • 4
    Publication Date: 1988-06-10
    Description: Previous studies involving platelet-derived growth factor (PDGF) have been based on the premise that a single cell-surface receptor binds all three isoforms of PDGF (AA, BB, and AB). It is now shown that two populations of PDGF receptor exist and can be distinguished by their ligand binding specificity. The B receptor binds only the BB dimer, whereas the A/B receptor binds AA, BB, and AB dimers. Human dermal fibroblasts appear to express seven times as much B receptor as A/B receptor. The B receptor is responsible for most PDGF receptor phosphorylation.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Hart, C E -- Forstrom, J W -- Kelly, J D -- Seifert, R A -- Smith, R A -- Ross, R -- Murray, M J -- Bowen-Pope, D F -- DE07063-11/DE/NIDCR NIH HHS/ -- GM35501/GM/NIGMS NIH HHS/ -- HL18645/HL/NHLBI NIH HHS/ -- New York, N.Y. -- Science. 1988 Jun 10;240(4858):1529-31.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Pathology, University of Washington, Seattle 98195.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/2836952" target="_blank"〉PubMed〈/a〉
    Keywords: Binding, Competitive ; Cell Membrane/metabolism ; Cells, Cultured ; Fibroblasts/metabolism ; Humans ; Kinetics ; Platelet-Derived Growth Factor/*metabolism ; Receptors, Cell Surface/*metabolism ; Receptors, Platelet-Derived Growth Factor ; Skin/*metabolism ; Structure-Activity Relationship
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  • 5
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    American Association for the Advancement of Science (AAAS)
    Publication Date: 1988-11-25
    Description: The human immunodeficiency virus type 1 (HIV-1) shows extensive genetic variation and undergoes rapid evolution. The fidelity of purified HIV-1 reverse transcriptase was measured during DNA polymerization in vitro by means of three different assays. Reverse transcriptase from HIV-1 introduced base-substitution errors in DNA from the bacteriophage phi X174 amber3 at estimated frequencies of 1/2000 to 1/4000. Analyses of misincorporation rates opposite a single template adenine residue showed that HIV-1 reverse transcriptase catalyzed nucleotide mismatches with a specificity of A:C much greater than A:G greater than A:A. The high error rate of HIV-1 reverse transcriptase in vitro translates to approximately five to ten errors per HIV-1 genome per round of replication in vivo. This high error rate suggests that misincorporation by HIV-1 reverse transcriptase is, at least in part, responsible for the hypermutability of the AIDS virus. The specificity of misincorporation may provide a basis for the systematic construction of antiviral nucleosides.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Preston, B D -- Poiesz, B J -- Loeb, L A -- CA-07263-03/CA/NCI NIH HHS/ -- N01AI72654/AI/NIAID NIH HHS/ -- R35-CA-39903/CA/NCI NIH HHS/ -- New York, N.Y. -- Science. 1988 Nov 25;242(4882):1168-71.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Pathology, University of Washington, Seattle 98195.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/2460924" target="_blank"〉PubMed〈/a〉
    Keywords: Avian Myeloblastosis Virus/enzymology ; Bacteriophage phi X 174/genetics ; DNA/*biosynthesis ; DNA Polymerase II/metabolism ; DNA, Viral/biosynthesis ; Electrophoresis, Polyacrylamide Gel ; HIV/*enzymology/genetics ; Kinetics ; Moloney murine leukemia virus/enzymology ; Mutation ; Nucleotides/metabolism ; RNA-Directed DNA Polymerase/*metabolism
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  • 6
    Publication Date: 1988-12-16
    Description: The fidelity of protein biosynthesis in any cell rests on the accuracy of aminoacylation of tRNA. The exquisite specificity of this reaction is critically dependent on the correct recognition of tRNA by aminoacyl-tRNA synthetases. It is shown here that the relative concentrations of a tRNA and its cognate aminoacyl-tRNA synthetase are normally well balanced and crucial for maintenance of accurate aminoacylation. When Escherichia coli Gln-tRNA synthetase is overproduced in vivo, it incorrectly acylates the supF amber suppressor tRNA(Tyr) with Gln. This effect is abolished when the intracellular concentration of the cognate tRNA(Gln2) is also elevate. These data indicate that the presence of aminoacyl-tRNA synthetase and the cognate tRNAs in complexed form, which requires the proper balance of the two macromolecules, is critical in maintaining the fidelity of protein biosynthesis. Thus, limits exist on the relative levels of tRNAs and aminoacyl-tRNA synthetases within a cell.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Swanson, R -- Hoben, P -- Sumner-Smith, M -- Uemura, H -- Watson, L -- Soll, D -- New York, N.Y. -- Science. 1988 Dec 16;242(4885):1548-51.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT 06511.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/3144042" target="_blank"〉PubMed〈/a〉
    Keywords: Amino Acyl-tRNA Synthetases/genetics/*metabolism ; Escherichia coli/enzymology/*genetics ; Kinetics ; Plasmids ; RNA, Transfer, Amino Acid-Specific/*metabolism ; RNA, Transfer, Gln/*metabolism ; beta-Galactosidase/genetics/metabolism
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  • 7
    Publication Date: 2006-04-15
    Description: We present an atomic-level description of the reaction chemistry of an enzyme-catalyzed reaction dominated by proton tunneling. By solving structures of reaction intermediates at near-atomic resolution, we have identified the reaction pathway for tryptamine oxidation by aromatic amine dehydrogenase. Combining experiment and computer simulation, we show proton transfer occurs predominantly to oxygen O2 of Asp(128)beta in a reaction dominated by tunneling over approximately 0.6 angstroms. The role of long-range coupled motions in promoting tunneling is controversial. We show that, in this enzyme system, tunneling is promoted by a short-range motion modulating proton-acceptor distance and no long-range coupled motion is required.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Masgrau, Laura -- Roujeinikova, Anna -- Johannissen, Linus O -- Hothi, Parvinder -- Basran, Jaswir -- Ranaghan, Kara E -- Mulholland, Adrian J -- Sutcliffe, Michael J -- Scrutton, Nigel S -- Leys, David -- New York, N.Y. -- Science. 2006 Apr 14;312(5771):237-41.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Manchester Interdisciplinary Biocentre, University of Manchester, Jackson's Mill, Post Office Box 88, Manchester M60 1QD, UK.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/16614214" target="_blank"〉PubMed〈/a〉
    Keywords: Alcaligenes faecalis/*enzymology ; Aspartic Acid/chemistry ; Binding Sites ; Catalysis ; Chemistry, Physical ; Computer Simulation ; Crystallography, X-Ray ; Kinetics ; Models, Chemical ; Motion ; Oxidation-Reduction ; Oxidoreductases Acting on CH-NH Group Donors/*chemistry/*metabolism ; Oxygen/chemistry ; Physicochemical Phenomena ; *Protons ; Temperature ; Thermodynamics ; Tryptamines/*metabolism ; Water/chemistry
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  • 8
    Publication Date: 2006-04-08
    Description: Intercellular flow of the phytohormone auxin underpins multiple developmental processes in plants. Plant-specific pin-formed (PIN) proteins and several phosphoglycoprotein (PGP) transporters are crucial factors in auxin transport-related development, yet the molecular function of PINs remains unknown. Here, we show that PINs mediate auxin efflux from mammalian and yeast cells without needing additional plant-specific factors. Conditional gain-of-function alleles and quantitative measurements of auxin accumulation in Arabidopsis and tobacco cultured cells revealed that the action of PINs in auxin efflux is distinct from PGP, rate-limiting, specific to auxins, and sensitive to auxin transport inhibitors. This suggests a direct involvement of PINs in catalyzing cellular auxin efflux.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Petrasek, Jan -- Mravec, Jozef -- Bouchard, Rodolphe -- Blakeslee, Joshua J -- Abas, Melinda -- Seifertova, Daniela -- Wisniewska, Justyna -- Tadele, Zerihun -- Kubes, Martin -- Covanova, Milada -- Dhonukshe, Pankaj -- Skupa, Petr -- Benkova, Eva -- Perry, Lucie -- Krecek, Pavel -- Lee, Ok Ran -- Fink, Gerald R -- Geisler, Markus -- Murphy, Angus S -- Luschnig, Christian -- Zazimalova, Eva -- Friml, Jiri -- New York, N.Y. -- Science. 2006 May 12;312(5775):914-8. Epub 2006 Apr 6.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Institute of Experimental Botany, the Academy of Sciences of the Czech Republic, 165 02 Prague 6, Czech Republic.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/16601150" target="_blank"〉PubMed〈/a〉
    Keywords: ATP-Binding Cassette Transporters/genetics/metabolism ; Arabidopsis/cytology/growth & development/*metabolism/physiology ; Arabidopsis Proteins/genetics/*metabolism ; Biological Transport ; Cell Membrane/metabolism ; Cells, Cultured ; Gravitropism ; HeLa Cells ; Humans ; Indoleacetic Acids/*metabolism ; Kinetics ; Membrane Transport Proteins/genetics/*metabolism ; Mutation ; Naphthaleneacetic Acids/metabolism ; Phthalimides/pharmacology ; Plant Roots/physiology ; Saccharomyces cerevisiae/genetics ; Tobacco ; Transfection ; Transformation, Genetic
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  • 9
    Publication Date: 1988-10-14
    Description: Suspensions of thymocytes from young rats were incubated with 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), which resulted in a sustained increase in cytosolic free Ca2+ concentration followed by DNA fragmentation and loss of cell viability. Both the Ca2+ increase and DNA fragmentation were prevented in cells treated with the inhibitor of protein synthesis, cycloheximide, and DNA fragmentation and cell killing were not detected when cells were incubated in a "Ca2+-free" medium or pretreated with high concentrations of the calcium probe, quin-2 tetraacetoxymethyl ester. These results indicate that TCDD can kill immature thymocytes by initiating a suicide process similar to that previously described for glucocorticoid hormones.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉McConkey, D J -- Hartzell, P -- Duddy, S K -- Hakansson, H -- Orrenius, S -- New York, N.Y. -- Science. 1988 Oct 14;242(4876):256-9.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Toxicology, Karolinska Institutet, Stockholm, Sweden.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/3262923" target="_blank"〉PubMed〈/a〉
    Keywords: Aminoquinolines ; Animals ; Calcium/metabolism/*pharmacology ; Cell Survival/drug effects ; Cycloheximide/pharmacology ; Cytosol/metabolism ; DNA/metabolism ; Deoxyribonuclease I/*metabolism ; Dioxins/*pharmacology ; Enzyme Activation/drug effects ; Fluorescent Dyes ; Glucocorticoids/pharmacology ; Kinetics ; Rats ; T-Lymphocytes/drug effects ; Tetrachlorodibenzodioxin/*pharmacology ; Thymus Gland/*drug effects/metabolism
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  • 10
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    American Association for the Advancement of Science (AAAS)
    Publication Date: 1988-04-29
    Description: The kinetics of calcium release by inositol 1,4,5-trisphosphate (IP3) in permeabilized rat basophilic leukemia cells were studied to obtain insight into the molecular mechanism of action of this intracellular messenger of the phosphoinositide cascade. Calcium release from intracellular storage sites was monitored with fura-2, a fluorescent indicator. The dependence of the rate of calcium release on the concentration of added IP3 in the 4 to 40 nM range showed that channel opening requires the binding of at least three molecules of IP3. Channel opening occurred in the absence of added adenosine triphosphate, indicating that IP3 acts directly on the channel or on a protein that gates it. The channels were opened by IP3 in less than 4 seconds. The highly cooperative opening of calcium channels by nanomolar concentrations of IP3 enables cells to detect and amplify very small changes in the concentration of this messenger in response to hormonal, sensory, and growth control stimuli.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Meyer, T -- Holowka, D -- Stryer, L -- AI22449/AI/NIAID NIH HHS/ -- GM24032/GM/NIGMS NIH HHS/ -- GM30387/GM/NIGMS NIH HHS/ -- New York, N.Y. -- Science. 1988 Apr 29;240(4852):653-6.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Cell Biology, Sherman Fairchild Center, Stanford University School of Medicine, CA 94305.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/2452482" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Basophils ; Benzofurans ; Calcimycin/pharmacology ; Calcium/*metabolism ; Cell Membrane Permeability ; Cytoplasm/metabolism ; Fluorescent Dyes ; Fura-2 ; Inositol 1,4,5-Trisphosphate ; Inositol Phosphates/metabolism/*pharmacology ; Ion Channels/drug effects/*metabolism ; Kinetics ; Leukemia, Experimental/metabolism ; Rats ; Spectrometry, Fluorescence ; Sugar Phosphates/*pharmacology ; Tumor Cells, Cultured
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