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  • International Union of Crystallography (IUCr)  (4,260)
  • 2015-2019
  • 1995-1999  (4,260)
  • 1999  (2,258)
  • 1998  (2,002)
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  • 2015-2019
  • 1995-1999  (4,260)
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  • 1
    Electronic Resource
    Electronic Resource
    Copenhagen : International Union of Crystallography (IUCr)
    Acta crystallographica 54 (1998), S. 8-15 
    ISSN: 1399-0047
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Numerous reports have been published in the literature which describe the crystallization of macromolecules by a variety of crystallization methods, including the vapour-diffusion and microbatch techniques. This topical review compares the results of examples of proteins which were crystallized by both vapour-diffusion and microbatch methods. The inherent features of the vapour-diffusion and microbatch methods are discussed and some specific conditions where one method appears more favourable than the other are reported. Guidelines for the conversion of crystallization conditions from vapour diffusion to microbatch (and vice versa) are also presented.
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  • 2
    Electronic Resource
    Electronic Resource
    Copenhagen : International Union of Crystallography (IUCr)
    Acta crystallographica 54 (1998), S. 74-80 
    ISSN: 1399-0047
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: The effects of a temperature increase on monoclinic and tetragonal lysozyme single crystals were investigated by polarizing microscopy, X-ray diffraction and laser Raman spectroscopy. To prevent dissolution, the mother liquor was removed, and the crystals were covered by the oil poly-(chlorotrifluoroethylene). Upon heating, their macroscopic shape was stable beyond 453 K but a change (or loss) of birefringence was observed around 352 and 367 K for the tetragonal and monoclinic crystal forms, respectively, which is associated with tighter packing and higher crystal forces in monoclinic lysozyme. Raman spectral changes in the amide I and amide III regions indicated denaturation of the protein within the crystalline environment at temperature where birefringence changes, and differences in the S—S band suggest that in monoclinic lysozyme, denaturation is accompanied with disruption of some S—S bonds. Comparison with thermal denaturation and gel formation (\beta-aggregation) of lysozyme in solution indicates that intermolecular interactions are mainly involved in the stabilization of the denatured lysozyme crystals. The behavior of ribonuclease A is very different. This protein unfolds and refolds reversibly in solution and its crystals melt at the unfolding temperature at 333 K, i.e. loss of structure induces breakdown of crystal lattice and macroscopic shape. Although the crystal lattice of proteins is stabilized by only few intermolecular contacts, its breakdown with increasing temperature is primarily a result of thermal unfolding of the polypeptide chains.
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  • 3
    ISSN: 1399-0047
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: The primary receptor (PotF) of the putrescine transport system in E. coli has been crystallized by the hanging-drop vapor-diffusion technique. The crystals belong to the space group P21212 with unit-cell dimensions a = 269.4, b = 82.33 and c = 93.74 Å. The crystals diffract beyond 2.2 Å with a rotating-anode X-ray source. A complete data set from the native crystals has been collected and processed at 2.3 Å resolution. Two heavy-atom derivatives have been prepared from the same Pt compound at 293 and 277 K. The difference Patterson maps revealed completely different major heavy-atom sites between these two derivatives.
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  • 4
    Electronic Resource
    Electronic Resource
    Copenhagen : International Union of Crystallography (IUCr)
    Acta crystallographica 54 (1998), S. 140-142 
    ISSN: 1399-0047
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: The histidine-containing phosphotransfer (HPt) domain at the C-terminus of the anaerobic sensor kinase ArcB has been cocrystallized with the chemotaxis response regulator CheY by a hanging-drop vapor-diffusion method. Crystals belong to space group P212121 with unit-cell dimensions a = 55.32, b = 76.29 and c = 83.89 Å, with one molecule in the crystallographic asymmetric unit. The crystals diffract to 2.7 Å resolution. This is the first crystallization of a protein–protein complex formed by a transmitter domain of sensor kinase and a receiver domain of response regulator in the two-component signal-transduction system.
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  • 5
    ISSN: 1399-0047
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Crystals of the monomeric and dimeric forms of human neutrophil gelatinase associated lipocalin have been grown in hanging-drop vapor-diffusion trials using PEG as a precipitating agent with recombinant protein expressed in a baculovirus-based system. Crystals of monomeric NGAL belong to the cubic space group P432 with lattice constants a = b = c = 126.6 Å; crystals of dimeric NGAL belong to the tetragonal space group P41212 (or its enantiomorph P43212) with lattice constants a = b = 54.14 and c = 121.56 Å. Isomorphous crystals of the NGAL dimer can be grown in the presence of ligand: the tripeptide N-formyl-Met-Leu-Phe.
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  • 6
    Electronic Resource
    Electronic Resource
    Copenhagen : International Union of Crystallography (IUCr)
    Acta crystallographica 54 (1998), S. 90-92 
    ISSN: 1399-0047
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Recent work has shown that Scilla campanulata agglutinin from bluebell bulbs has a strong affinity for α(1,3)- and α(1,6)-linked mannosyl residues and possesses moderate antiretroviral activity. This lectin has been crystallized by the hanging-drop method of vapour diffusion complexed with the disaccharide mannose-α1,6-D-mannose. The crystals are in the space group P21212 with unit-cell dimensions a = 70.63, b = 92.79 and c = 47.25 Å, and with a dimer in the asymmetric unit. The crystals diffract X-rays to beyond 1.5 Å resolution at 277 K and are stable in an X-ray beam. Data to 1.6 Å resolution have been collected using a MAR image-plate system at a synchrotron source and the structure of the complex has been solved by the molecular replacement method.
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  • 7
    Electronic Resource
    Electronic Resource
    Copenhagen : International Union of Crystallography (IUCr)
    Acta crystallographica 54 (1998), S. 108-110 
    ISSN: 1399-0047
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Profilin is an actin-monomer binding protein that regulates the distribution and dynamics of the actin cytoskeleton. Profilin binds poly-L-proline and proline-rich peptides in vitro and co-localizes with proline-rich proteins in focal adhesions and at the site of actin tail assembly on the surface of intracellular parasites such as Listeria monocytogenes. The crystallization of the complex between human platelet profilin (HPP) and an L-proline decamer [(Pro)10] is reported here. Diffraction from these crystals is consistent with the space group P21212 with unit-cell constants a = 68.25, b = 97.64, c = 39.10 Å. The crystals contain two HPP molecules per asymmetric unit and diffract to 2.2 Å.
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  • 8
    Electronic Resource
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    Copenhagen : International Union of Crystallography (IUCr)
    Acta crystallographica 54 (1998), S. 111-113 
    ISSN: 1399-0047
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Functional monomeric 83 kDa sialidase L, a NeuAcα2→3Gal-specific sialidase from Macrobdella leech, was expressed in Escherichia coli and readily crystallized by a macroseeding technique. The crystal belongs to space group P1 with unit-cell parameters a = 46.4, b = 69.3, c = 72.5 Å, α = 113.5, β = 95.4 and γ = 107.3°. There is one molecule per unit cell, giving a Vm = 2.4 Å3 Da−1 and a solvent content of 40%. Native and mercury-derivative data sets were collected to 2.0 Å resolution. Threading and molecular-replacement calculations confirmed the existence of a bacterial sialidase-like domain.
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  • 9
    ISSN: 1399-0047
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: The catalytic domain of the CeIF processive endocellulase, a family 48 glycosyl hydrolase from Clostridium cellulolyticum has been crystallized in the presence of a newly synthesized inhibitor (methyl 4-S-β-cellobiosyl-4-thio-β-cellobioside), by vapour diffusion, using PEG as a precipitant. The protein crystallizes in the orthorhombic P212121 space group and diffracts to a resolution of 2.0 Å. The unit-cell parameters are a = 61.4, b = 84.5, c = 121.9 Å.
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  • 10
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    Copenhagen : International Union of Crystallography (IUCr)
    Acta crystallographica 54 (1998), S. 451-453 
    ISSN: 1399-0047
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Crystals of the human MHC-encoded molecule MICA, a homologue of MHC class I proteins, have been grown in hanging-drop vapor-diffusion trials using ammonium sulfate as a precipitating agent with recombinant protein expressed in a baculovirus-based system. Cryo-preserved crystals of MICA belong to the cubic space group F4132 with lattice constants a = b = c = 260.7 Å and diffract to a resolution limit of 3.0 Å when cryo-preserved. These crystals do not diffract when handled conventionally.
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  • 11
    ISSN: 1399-0047
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: The thermostable catechol 2,3-dioxygenase of Bacillus stearothermophilus has been crystallized. The crystal is probably in the space group I222 with unit-cell dimensions of a = 70.87, b = 74.60 and c = 133.69 Å. A native data set has been collected with a completeness of 96% at 2.22 Å resolution and an Rmerge value of 0.091.
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  • 12
    ISSN: 1399-0047
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Thiaminase I (Mr = 42 100) from B. thiaminolyticus, expressed in E. coli, has been crystallized by the vapor-diffusion method. Three crystal forms, two of which grew from 0.1 M sodium acetate (pH = 4.6), 0.2 M ammonium sulfate and 30%(w/v) PEG 2000, have been examined by X-ray analysis. One crystal form diffracted to 2.5 Å at room temperature, was orthorhombic, and had unit-cell edges of a = 87.7, b = 120.5 and c = 76.7 Å with space group P212121. A self-Patterson map showed a strong peak indicating noncrystallographic translational pseudosymmetry with (u, v, w) = (0.03, 0.0, 0.5). When these crystals were frozen at liquid-nitrogen temperatures, a second crystal form was observed which had unit-cell dimensions a = 85.5, b = 117.5 and c = 36.6 Å with space group P21212. A third crystal form grew from 0.1 M Tris (pH = 8.5), 0.2 M sodium acetate trihydrate and 28%(w/v) PEG 6000 to produce orthorhombic crystals of space group P212121 with cell edges of a = 114.4, b = 123.1 and c = 92.5 Å.
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  • 13
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    Copenhagen : International Union of Crystallography (IUCr)
    Acta crystallographica 54 (1998), S. 454-457 
    ISSN: 1399-0047
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: A new crystal form of the vanadium-dependent bromoperoxidase from Corallina officinalis has been obtained. The crystals exhibit a `teardrop' morphology and are grown from 2 M ammonium dihydrogen phosphate pH 5 and diffract to beyond 1.7 Å resolution. They are in tetragonal space group P4222 with unit-cell dimensions of a = b = 201.9, c = 178.19 Å, α = β = γ = 90°. A 2.3 Å resolution native data set has been collected at the Hamburg Synchrotron. A mercury derivative data set has also been collected, and the heavy-atom positions have been determined. The self-rotation function and the positions of the heavy atoms are consistent with the molecule being a dodecamer with local 23 symmetry.
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  • 14
    Electronic Resource
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    Copenhagen : International Union of Crystallography (IUCr)
    Acta crystallographica 54 (1998), S. 458-460 
    ISSN: 1399-0047
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Human glutathione-S-transferase M2–2 (hGSTM2–2) was expressed in Escherichia coli and purified by GSH-affinity chromatography. The recombinant enzyme and the protein isolated from human tissue were indistinguishable based on physicochemical, enzymatic and immunological criteria. The catalytically active dimeric hGSTM2–2 was crystallized without GSH or other active-site ligands in two crystal forms. Diffraction from form A crystals extends to 2.5 Å and is consistent with the space group P21 (a = 53.9, b = 81.5, c = 55.6 Å, β = 109.26 Å) with two monomers in the asymmetric unit. Diffraction from form B crystals extends to 3 Å and is consistent with a space group P212121 (a = 57.2, b = 80.7, c = 225.9 Å) with two dimers in the asymmetric unit. This is the first report of ligand-free mu-class GST crystals, and a comparison with liganded complexes will provide insight into the structural consequences of substrate binding which are thought to be important for catalysis.
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  • 15
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    Copenhagen : International Union of Crystallography (IUCr)
    Acta crystallographica 54 (1998), S. 470-472 
    ISSN: 1399-0047
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: A procedure for the crystallization of recombinant cytochrome P450cam has been developed which avoids the difficulties inherent in the glass-capillary free-interface diffusion method reported previously. The surface mutation, Cys334→Ala (C334A), originally designed to prevent dimer formation and thus improve routine handling of the enzyme, facilitates crystallization by the hanging-drop vapour-diffusion technique. Crystals of (C334A)P450cam grow within 48 h and diffract to beyond 1.2 Å at 100 K in-house on a Siemens multiwire area detector. Data have been collected from the camphor-bound form to 1.35 Å.
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  • 16
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    Electronic Resource
    Copenhagen : International Union of Crystallography (IUCr)
    Acta crystallographica 54 (1998), S. 461-466 
    ISSN: 1399-0047
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Extended delineation of water molecules, monitored using Rfree values, afforded considerable improvement in quality of electron-density maps for structure determination of mammalian class I and E. coli class II aldolases. Augmented solvent definition results in an additional decrease in Rfree values of 3–4% and is reflected in significantly enhanced electron-density envelopes enabling tracing of amino-acid sequences through regions of otherwise discontinuous or weak electron density.
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  • 17
    ISSN: 1399-0047
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: The NADP-dependent β-keto acyl carrier protein reductase (BKR) from E. coli has been crystallized by the hanging-drop method of vapour diffusion using poly(ethylene glycol) of average molecular weight 1450. The crystals belong to the hexagonal space group P6122 or P6522 with unit-cell dimensions a = b = 67.8, c = 355.8 Å. Calculated values for Vm and consideration of the packing suggest that the asymmetric unit contains a dimer. BKR catalyses the first reductive step in the elongation cycle of fatty-acid biosynthesis. It shares extensive sequence homology with the enzyme which catalyzes the second reductive step in the cycle, enoyl acyl carrier protein reductase (ENR), and thus provides an opportunity to study the evolution of enzyme function in a metabolic pathway. The structure determination will permit the analysis of the molecular basis of its catalytic mechanism and substrate specificity.
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  • 18
    ISSN: 1399-0047
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Molecules of the human killer cell inhibitory receptor (KIR) family, which belong to the immunoglobulin superfamily (IgSF), are expressed on the surface of natural killer (NK) cells and some subsets of T cells. These receptors function to mediate the inhibition or activation of cytotoxic activity by recognizing HLA class I molecules on the target cell. The extracellular region of a p58 KIR specific for HLA-Cw1,3,7 (KIR2) has been overproduced in Escherichia coli and purified. The recombinant KIR2 has been crystallized in 9–10% poly(ethylene glycol) methyl ether (average Mr = 8000), 50mM HEPES, 8% ethylene glycol, 0.5% octyl-β-glucoside, pH 7.5, at 294 K using the sitting-drop vapour-diffusion method. Preliminary X-ray diffraction studies reveal the space group to be hexagonal (P6122 or P6522) with lattice constants a = b = 95.3, c = 130.8 Å. A native data set (3 Å resolution) has been collected at the Photon Factory (λ = 1.0 Å).
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  • 19
    Electronic Resource
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    Copenhagen : International Union of Crystallography (IUCr)
    Acta crystallographica 54 (1998), S. 436-436 
    ISSN: 1399-0047
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: HORF6 is a member of the novel antioxidant enzyme family found in humans. A recombinant form of hORF6 expressed and purified from E. coli has been crystallized by the hanging-drop method using various PEG's as precipitating agents. HORF6 crystallizes in two different monoclinic space groups, P21 and C2. The P21 crystals have unit-cell dimensions of a = 47.85, b = 75.17, c = 63.30 Å and β = 110.21° and contain two monomers per asymmetric unit, while the C2 crystals have unit-cell dimensions of a = 165.27, b = 95.44, c = 166.44 Å and β = 128.97° and contain more than six monomers per asymmetric unit. The P21 crystals with the smaller unit cell diffract X-rays better and behave well for the X-ray analysis. A native data set from a single crystal of the P21 space group gas been collected to 2.0 Å resolution.
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  • 20
    ISSN: 1399-0047
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Porphobilinogen synthase (PBGS) catalyzes the condensation of two identical substrate molecules, 5-aminolevulinic acid (ALA), in an asymmetric manner to form porphobilinogen. E. coli PBGS is an homooctameric enzyme. The number of active sites is not clear, but each subunit binds one ZnII ion and one MgII ion. Diffraction-quality crystals of native E. coli PBGS have been obtained, and unit-cell dimensions (a = 130.8, c = 144.0 Å) are reported. These crystals diffract to about 3.0 Å resolution.
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  • 21
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    Copenhagen : International Union of Crystallography (IUCr)
    Acta crystallographica 54 (1998), S. 441-443 
    ISSN: 1399-0047
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Bowman–Birk trypsin inhibitor from barley seeds has been crystallized at room temperature using polyethylene glycol as precipitant. The crystal is tetragonal, belonging to the space group P41212 (or P43212), with unit cell parameters of a = b = 62.48 and c = 94.63 Å. The asymmetric unit contains one molecule of Bowman–Birk trypsin inhibitor with corresponding crystal volume per protein mass (Vm) of 2.89 Å3 Da−1 and the solvent content of 57% by volume. The crystals diffract to at least 1.9 Å Bragg spacing upon exposure to synchrotron X-rays. X-ray data to 1.9 Å have been collected from a native crystal.
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  • 22
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    Copenhagen : International Union of Crystallography (IUCr)
    Acta crystallographica 54 (1998), S. 276-278 
    ISSN: 1399-0047
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Crystals of the α-hemolysin heptamer, a transmembrane pore-forming toxin from Staphylococcus aureus, have been grown using the nonionic detergents n-decyldimethyl- and n-decyldiethylphosphine oxide, phosphorus homologs of the ionic amine oxide detergents. Five crystal forms were obtained, one of which diffracted X-rays to 3 Å resolution. This crystal form displayed elements of pseudo mm symmetry in screened precession photographs yet it was triclinic with unit-cell dimensions a = 173, b = 173, c = 102 Å, α = 92.6, β = 94.8, γ = 90.2°.
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  • 23
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    Copenhagen : International Union of Crystallography (IUCr)
    Acta crystallographica 54 (1998), S. 269-272 
    ISSN: 1399-0047
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: The NAD+-dependent phenylalanine dehydrogenase from Nocardia sp239 has been crystallized by the hanging-drop method of vapour diffusion using ammonium sulfate as the precipitant. Two crystal forms were obtained in the presence and absence of the enzyme substrates phenylpyruvic acid or phenylalanine and its coenzyme NADH. Crystals of the native protein belong to the hexagonal system, with the space group being one of the enantiomorphic pair P6122 or P6522. The cell dimensions are a = b = 111.0, c = 174.5 Å, α = β = 90 and γ = 120°. Crystals grown from the protein co-crystallized with its substrates all belong to the trigonal system, space group P3121 or P3221, with unit-cell dimensions of a = b = 88.1 , c = 112.6 Å, α = β = 90 and γ = 120°. Preliminary protein-sequencing experiments have established that this enzyme is related to the octameric PheDH's which are members of the wider superfamily of amino-acid dehydrogenases. However, gel-filtration studies suggest that this enzyme is active as a monomer. The full determination of the three-dimensional structure of this phenylalanine dehydrogenase will add to the understanding of the molecular basis of the differential substrate specificity within this enzyme superfamily. In turn this will contribute to the rational design of an amino-acid dehydrogenase which could be used for the diagnosis of phenylketonuria and for the chiral synthesis of high-value pharmaceuticals.
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  • 24
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    Copenhagen : International Union of Crystallography (IUCr)
    Acta crystallographica 54 (1998), S. 662-664 
    ISSN: 1399-0047
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Allophycocyanin from red alga Porphyra yezoensis has been crystallized in three crystal forms. Form 1 crystals with space group P4132 or P4332 and cell parameters a = 286 Å, α = 90° were obtained by using isopropanol as precipitant. These crystals did not diffract beyond 5.8 Å and could not be used in structure analysis. Form 2 crystals were obtained when crystallization conditions were slightly changed by adding 0.2 M magnesium chloride. The space group of form 2 was not determined because it was difficult to get large single crystals. Form 3 crystals were obtained by using ammonium sulfate as precipitant. The space group of form 3 is R32 with cell dimensions a = b = 105.3, c = 189.4 Å and one \alpha\beta unit in the asymmetric unit. These crystals diffract up to 2.06 Å resolution and are suitable for structure determination by molecular-replacement methods.
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  • 25
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    Copenhagen : International Union of Crystallography (IUCr)
    Acta crystallographica 54 (1998), S. 675-677 
    ISSN: 1399-0047
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Pentaerythritol tetranitrate (PETN) reductase of Enterobacter cloacae PB2, a flavoprotein involved in the biodegradation of the explosive PETN, ethylene glycol dinitrate (EGDN) and glycerol trinitrate (GTN), was purified from an overexpressing strain of E. coli and crystallized at 293 K using the sitting-drop vapour-diffusion method. Diffraction data can be seen at 1.8 Å. The primitive orthorhombic cell has a monomer in the asymmetric unit. Preliminary molecular-replacement calculations have been performed using a search model based on Old Yellow enzyme.
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  • 26
    ISSN: 1399-0047
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Recombinant Sulfolobus solfataricus glyceraldehyde-3-phosphate dehydrogenase has been purified and found to be a tetramer of 148 kDa. The enzyme shows dual cofactor specificity and uses NADP+ in preference to NAD+. The sequence has been compared with other GAPDH proteins including those from other archaeal sources. The purified protein has been crystallized from ammonium sulfate to produce crystals that diffract to 2.4 Å with a space group of P43212 or P41212. A native data set has been collected to 2.4 Å using synchrotron radiation and cryocooling.
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  • 27
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    Copenhagen : International Union of Crystallography (IUCr)
    Acta crystallographica 54 (1998), S. 289-305 
    ISSN: 1399-0047
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: The crystal structure of the zinc-containing exopeptidase bovine carboxypeptidase A (CPA) has been refined to high resolution, based on a data set collected from a single crystal, incorporating new sequence information based on cloning of the bovine gene. In addition, new refined structures are available for the zinc-removed form of the enzyme, apo-CPA, as well as the mercury-replaced form, Hg-CPA. The native structure reveals that the zinc-bound water molecule does not appear to be more loosely bound than the rest of the zinc ligands, at least when B factor values are considered. Nor is there any evidence for a secondary location of this water molecule. The apo-enzyme structure does not show any density in the place of the removed zinc ion. The only significant change appears to be a χ2 rotation of one zinc histidine ligand to form an ion-pair interaction with a glutamic acid side chain. The structure of Hg-CPA reveals a solvent tris molecule bound to the mercury cation, as well as an unidentified cation bound to Glu270. The location of this cation agrees with previous proposals for the binding site of inhibitory zinc. These observations may explain some of the differences in kinetics observed in metal-replaced CPA.
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  • 28
    ISSN: 1399-0047
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Crystals of chloroplast NADP-dependent malate dehydrogenase have been grown both with and without the cofactor NADP present. The enzyme has a molecular weight of 43 kDa per subunit and exists as a dimer in solution. The crystals diffract to 2.8 Å and belong to the space group P3221 with cell dimensions a = 148.1, c = 65.5 Å.
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  • 29
    ISSN: 1399-0047
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Ribulose-1,5-bisphosphate carboxylase/oxygenase is the key enzyme for photosynthesis. The wild-type and mutant (amino-acid substitutions in the catalytically important loop 6 region) enzymes from Chlamydomonas reinhardtii, a unicellular green alga, were crystallized. Wild-type, single-mutant (V331A) and two double-mutant (V331A/T342I and V331A/G344S) proteins were activated with cofactors CO2 and Mg2+, complexed with the substrate analog 2′-carboxyarabinitol-1,5-bisphosphate, and crystallized in apparently isomorphous forms. Unit-cell determinations have been completed for three of the enzymes. They display orthorhombic symmetry with similar cell parameters: wild type a = 130.4, b = 203.3, c = 208.5 Å; single mutant (V331A) a = 128.0, b = 203.0, c = 207.0Å; and double mutant (V331A/T342I) a = 130.0, b = 202.1, c = 209.7 Å. Crystals of the wild-type and single-mutant (V331A) enzymes diffracted to \sim2.8 Å. A small crystal of the double-mutant (V331A/T342I) enzyme diffracted to \sim6 Å. A partial data set (68% complete) of the wild-type protein has been collected at room temperature to about 3.5 Å.
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  • 30
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    Copenhagen : International Union of Crystallography (IUCr)
    Acta crystallographica 54 (1998), S. 1017-1019 
    ISSN: 1399-0047
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: The water-soluble portion of rat heme oxygenase-1 which lacks 22 hydrophobic amino-acid residues at the C-terminus was expressed in E. coli and crystallized in the form of a complex with heme by the vapor-diffusion method using polyethylene glycol 4000 as the precipitant. The crystals belong to the tetragonal space group P41212 or P43212, with unit-cell dimensions of a = b = 56.7, c = 186.7 Å. The crystal contains one heme–heme oxygenase-1 complex in an asymmetric unit and diffracts X-rays beyond 3.0 Å resolution with a conventional X-ray source.
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  • 31
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    Copenhagen : International Union of Crystallography (IUCr)
    Acta crystallographica 54 (1998), S. 964-974 
    ISSN: 1399-0047
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Erabutoxin a has been crystallized in its monomeric and dimeric forms. The structures were refined at 1.50 and 1.49 Å resolution, respectively, using synchrotron radiation data. The crystals belong to space group P212121, with cell dimensions a = 49.84, b = 46.62, c = 21.22 Å for the monomer and a = 55.32, b = 53.54, c = 40.76 Å for the dimer. Using starting models from earlier structure determinations, the monomeric structure refined to an R value of 16.7% (8004 unique reflections, 17.0–1.50 Å resolution range), while the dimeric structure has been solved by the molecular-replacement method with a final R value of 16.9% (19444 unique reflections, 17.4–1.49 Å resolution range). The high-resolution electron-density maps clearly revealed significant discrete disorder in the proteins and allowed an accurate determination of the solvent structure. For the monomer, the side chains of six residues were modelled with alternate conformers and 106 sites for water molecules and one site for a sulfate ion were included in the final model, whereas for the dimer, 206 sites for water molecules were included and both C-terminal residues together with the side chains of 11 residues adopted alternative conformations. A comparison was made with earlier structure determinations. The features of the solvent structure of the erabutoxin molecules are discussed in detail.
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  • 32
    ISSN: 1399-0047
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Glutamate decarboxylase (GAD) is a vitamin B6 enzyme which catalyzes the α-decarboxylation of L-glutamate to γ-aminobutyric acid (GABA). Escherichia coli cells coexpress two highly homologous enzyme isoforms, GADα and GADβ. Well diffracting crystals of GADβ were obtained by taking advantage of the possibility of expressing each isoform separately. They belong to space group P31 or P32 with the unit-cell dimensions a = b = 115.6 and c = 206.6 Å and contain one GAD hexamer in the asymmetric unit. High-resolution synchrotron data were collected at 100 K for the native protein and a potential heavy-atom derivative.
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  • 33
    ISSN: 1399-0047
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Crystals of alcohol dehydrogenase from Sulfolobus solfataricus were grown in the Advanced Protein Crystallization Facility during the Life and Microgravity Sciences Spacelab mission on the US Space Shuttle. Large diffracting crystals were obtained by dialysis, whereas only poor-quality crystals were obtained by vapour diffusion. The quality of both the microgravity and ground-based crystals was analysed by X-ray diffraction. There was some improvement in terms of size and diffraction resolution limit for the microgravity crystals. However, the twinning observed in the Earth-grown crystals was also present for those grown in microgravity.
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  • 34
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    Copenhagen : International Union of Crystallography (IUCr)
    Acta crystallographica 54 (1998), S. 400-402 
    ISSN: 1399-0047
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: A method for locating heavy atoms in the unit cell of macromolecular crystals by a full-symmetry translation function is described. The approach has been implemented in the program TRAHALO and tested on experimental isomorphous and anomalous data.
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  • 35
    ISSN: 1399-0047
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Recombinant aspartate aminotransferase from an extremely thermophilic bacterium, Thermus thermophilus HB8, has been crystallized in two different crystal forms. The crystals of both forms are orthorhombic and belong to space group P212121 with cell dimensions a = 124.3, b = 113.6 and c = 61.6 Å for form I and a = 197.3, b = 109.7 and c = 80.3 Å for form II. The crystals of form I and II diffract to 2.1 and 2.5 Å resolution, respectively, on a conventional laboratory rotating-anode source. Two heavy-atom derivatives have been identified for form I.
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  • 36
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    Copenhagen : International Union of Crystallography (IUCr)
    Acta crystallographica 54 (1998), S. 989-990 
    ISSN: 1399-0047
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Creatine kinase (E.C. 2.3.7.2) is an important enzyme in energy metabolism which catalyzes the reversible transfer of a phosphoryl group between phosphocreatine and ADP to give ATP. Large quantities of a brain-type creatine kinase have been isolated from bovine photoreceptor cells and crystals suitable for X-ray diffraction analysis have been obtained by hanging-drop vapor diffusion. Crystals grow as tetragonal bipyramids in space group P43212 with cell dimensions a = b = 96.49, c = 108.42 Å and diffract to at least 2.7 Å resolution.
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  • 37
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    Copenhagen : International Union of Crystallography (IUCr)
    Acta crystallographica 54 (1998), S. 991-993 
    ISSN: 1399-0047
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: The plant aspartic proteinase cardosin A was crystallized using vapour diffusion. Crystals belong to the monoclinic space group C2, cell dimensions a = 116.9 (2), b = 87.2 (8), c = 81.3 (1) Å, β = 104.4 (4)°, and contain two molecules in the asymmetric unit related by a non-crystallographic twofold axis. Diffraction data were collected at room temperature with radiation from a synchrotron source up to 2.85 Å resolution. When the crystals were flash cooled to 110 K in a nitrogen stream the same resolution limit could also be obtained on a rotating-anode source. Recently, synchrotron radiation together with flash cooling led to an improvement of the diffraction data to 1.72 Å resolution.
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  • 38
    ISSN: 1399-0047
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: The trimeric signal-transduction protein GlnK, from Escherichia coli, has been over-expressed, purified to homogeneity and crystallized. The crystals belong to space group P213 with a = 85.53 Å and have two subunits in the asymmetric unit. The complex of GlnK with ATP crystallized in space group P63 with a = 57.45 Å and c = 54.79 Å. These crystals have a single subunit in the asymmetric unit. High-quality diffraction data from crystals of GlnK and the GlnK complex have been collected to 2.0 Å.
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  • 39
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    Copenhagen : International Union of Crystallography (IUCr)
    Acta crystallographica 54 (1998), S. 994-995 
    ISSN: 1399-0047
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: The hyperthermostable DNA polymerase from a marine Thermococcus archaeon has been crystallized in space group P212121, with unit-cell dimensions a = 94.8, b = 98.2, c = 112.2 Å with one molecule per asymmetric unit. Conditions for data collection at 98 K have been identified, and a complete data set was collected to 2.2 Å resolution. Strategies employed here may facilitate crystallization of other hyperthermostable proteins. The structure of this enzyme will provide the first structural data on the archaeal and hyperthermostable classes of DNA polymerases. Sequence homology to human polymerase \alpha (polymerase B family) may make it a model for studying eukaryotic and viral polymerases and for the development of anti-cancer and anti-viral therapeutics.
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  • 40
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    Copenhagen : International Union of Crystallography (IUCr)
    Acta crystallographica 54 (1998), S. 999-1001 
    ISSN: 1399-0047
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Crystallization of the hydrophilic ectodomain of the epidermal growth factor (EGF) receptor has been accomplished in the presence of the ligand EGF. Two different crystal forms have been obtained, one of which was suitable for X-ray analysis. The space group of this form has been assigned to P21212 with unit-cell dimensions of a = 207.4, b = 113.3 and c = 120.4 Å. A native data set has been recorded and a heavy-atom search is currently under way. Diffraction from these crystals, however, is limited to low resolution and extensive trials to improve crystal quality further have all failed. To analyse the molecular shape and aggregation of the receptor protein in solution, small-angle X-ray diffraction and dynamic light-scattering techniques have been applied. Synchrotron radiation in combination with cryo-techniques is essential for data collection because of the high solvent content and radiation sensitivity.
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  • 41
    ISSN: 1399-0047
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: The thermophilic and thermostable family B DNA polymerase from the archaeon Sulfolobus solfataricus (Mr of about 100 kDa) has been crystallized by the hanging-drop vapour-diffusion method at 294 K using ammonium sulfate as precipitant. The crystals belong to the monoclinic space group C2 with cell dimensions a = 187.4, b = 68.5, c = 125.8 Å and β = 107.8° and diffract up to 2.7 Å resolution on a rotating-anode X-ray source. Native data have been collected at 100 K. A heavy-atom derivative search is in progress.
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  • 42
    ISSN: 1399-0047
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Meningococcal meningitis is a severe childhood disease which often results in significant disability or death. Two major etiological agents of meningitis are the group B meningococci and capsular type K1 E. coli. The virulence of these organisms is attributable to structural mimicry between their common α(2–8)-polysialic acid capsular polysaccharide and human tissue antigens, which allows the bacteria to evade immune surveillance. There is currently no effective vaccine to protect against this infection. It has been demonstrated that the capsular polysaccharide of the bacteria can adopt a unique `antigenic conformation'. This antigenic conformation has formed the basis for the development of an N-propionylated polysialic acid vaccine. Immunization trials in mice with this vaccine show the production of two groups of antibodies, of which only N-propionylated polysialic acid-specific were protective. Knowledge of the structure of the antigen-binding site which recognizes the protective epitope is essential to determining the antigenic conformation of the polysaccharides, and is a critical aspect in understanding and improving the action of potential vaccines. The antigen-binding fragments (Fab) of one protective (13D9) and one non-protective (6B9) monoclonal antibody specific for the capsular polysaccharides of group B meningococci have been crystallized and have undergone preliminary X-ray diffraction analysis. Both crystals are observed to scatter X-rays to approximately 1.7 Å resolution at the A1 station at the Cornell High-Energy Synchrotron Source. 13D9 has an orthorhombic unit cell with a = 41.8, b = 102.3, c = 134.7 Å, with space group P212121. Fab 6B9 has an orthorhombic unit cell with a = 89.6, b = 132.0 and c = 36.9 Å, with space group P21212.
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  • 43
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    Acta crystallographica 54 (1998), S. 1008-1011 
    ISSN: 1399-0047
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Portal proteins are cyclical oligomers which play essential roles in bacteriophage pro-capsid formation, DNA packaging, and in connector formation. Bacteriophage SPP1 portal protein (gp6) is a turbine-like molecule with 13-fold symmetry [Dube et al. (1993) EMBO J. 12, 1303–1309]. The purified protein was crystallized with polyethylene glycol 400 as the precipitating agent using the vapor-diffusion method. Salt conditions were selected based on the properties of gp6 in different ionic environments. X-ray diffraction data up to a resolution of 7.85 Å were measured from frozen crystals with orthorhombic space group C2221 and cell dimensions a = 180.5 (5), b = 223.5 (5), c = 417 (1) Å. The asymmetric unit contains one tridecameric portal protein with 57.3 kDa subunits. The self-rotation searches confirm the 13-fold symmetry of the crystallized protein.
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  • 44
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    Copenhagen : International Union of Crystallography (IUCr)
    Acta crystallographica 54 (1998), S. 1014-1016 
    ISSN: 1399-0047
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Pap1 is a fission yeast transcription factor that activates genes related with resistance against staurosporine, a potent inhibitor of protein kinase C, and has been shown to be involved in cell growth, cell cycle, carcinogenesis and differentiation. Pap1 has the bZIP DNA-binding domain but binds to non-consensus DNA sequences for the bZIP motif. Highly ordered crystals of the DNA-binding domain complexed with a DNA fragment that has an ATF/CREB-like non-consensus sequence have been obtained. The crystals grew by the vapor-diffusion technique with polyethylene glycol 6000 and belong to space group R3 with a = b = 240.78, c = 43.85 Å. A 2.0 Å resolution data set was collected with a cryo-crystallographic technique.
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  • 45
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    Acta crystallographica 54 (1998), S. 1012-1013 
    ISSN: 1399-0047
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Recombinant citrate synthase from a psychrotolerant bacterium, DS2–3R, recently isolated in Antarctica, has been crystallized. The crystals belong to space group P6122 or P6522, with cell dimensions a = b = 70.8, c = 307.8 Å. Diffraction data collected on a synchrotron from a cryoprotected crystal extend to at least 2.0 Å. Knowledge of the structure of this enzyme will add to the understanding of cold activity and thermolability, and will be of biotechnological interest. Previously, the structure of citrate synthase from Archaea inhabiting environments at 328 and 373 K, has been reported. This present study will extend our understanding of the structural integrity and activity of proteins at the temperature extremes of life.
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  • 46
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    Copenhagen : International Union of Crystallography (IUCr)
    Acta crystallographica 55 (1999), S. 4-4 
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    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
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  • 47
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    Acta crystallographica 55 (1999), S. 5-7 
    ISSN: 1399-0047
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Significant improvement in the resolution and quality of the X-ray diffraction of crystals of MTCP-1 protein was observed on post-crystallization soaking. The MTCP-1 crystals grown from 1.5 M ammonium sulfate diffracted to only 3.0 Å resolution with some disorder in the diffraction. After post-crystallization soaking in a solution containing 2.0 M ammonium sulfate, the disorder was eliminated and diffraction extended to better than 2.0 Å resolution. Both native and selenomethionine-enriched crystals demonstrated better diffraction after soaking for several months. This simple technique may be useful to improve the diffraction quality of protein crystals generally.
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  • 48
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    Copenhagen : International Union of Crystallography (IUCr)
    Acta crystallographica 55 (1999), S. 25-30 
    ISSN: 1399-0047
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: The crystal structure of a bifunctional inhibitor of α-amylase and trypsin from the seeds of ragi (Indian finger millet, Eleusine coracana Gaertneri) has been determined by an X-ray diffraction method. The inhibitor consists of 122 amino acids with five disulfide bridges and belongs to the plant α-amylase/trypsin-inhibitor family. This is the first crystal structure determination of a member of this family. The protein, purified from the seeds of ragi, has a molecular mass of 13300 Da with a pI of 10.3. Crystals were grown by a microdialysis method using ammonium sulfate as precipitant. The improved purification protocol and the modified crystallization conditions enabled reproducible growth of the crystals. The cell parameters are a = 41.2, b = 47.4, c = 55.9 Å. The intensity data were collected to 2.9 Å resolution, and the crystal structure was determined using the molecular-replacement method. The structure was refined using the X-PLOR and CCP4 program packages to a conventional R factor of 21%. The structure contains four α-helices between residues 19–29, 37–51, 56–65 and 90–95, and two short antiparallel β-strands between residues 67–70 and 73–75.
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  • 49
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    Acta crystallographica 55 (1999), S. 8-24 
    ISSN: 1399-0047
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Carbamoyl phosphate synthetase catalyzes the formation of carbamoyl phosphate from one molecule of bicarbonate, two molecules of Mg2+ATP and one molecule of glutamine or ammonia depending upon the particular form of the enzyme under investigation. As isolated from Escherichia coli, the enzyme is an \alpha,β-heterodimer consisting of a small subunit that hydrolyzes glutamine and a large subunit that catalyzes the two required phosphorylation events. Here the three-dimensional structure of carbamoyl phosphate synthetase from E. coli refined to 2.1 Å resolution with an R factor of 17.9% is described. The small subunit is distinctly bilobal with a catalytic triad (Cys269, His353 and Glu355) situated between the two structural domains. As observed in those enzymes belonging to the \alpha/\beta-hydrolase family, the active-site nucleophile, Cys269, is perched at the top of a tight turn. The large subunit consists of four structural units: the carboxyphosphate synthetic component, the oligomerization domain, the carbamoyl phosphate synthetic component and the allosteric domain. Both the carboxyphosphate and carbamoyl phosphate synthetic components bind Mn2+ADP. In the carboxyphosphate synthetic component, the two observed Mn2+ ions are both octahedrally coordinated by oxygen-containing ligands and are bridged by the carboxylate side chain of Glu299. Glu215 plays a key allosteric role by coordinating to the physiologically important potassium ion and hydrogen bonding to the ribose hydroxyl groups of ADP. In the carbamoyl phosphate synthetic component, the single observed Mn2+ ion is also octahedrally coordinated by oxygen-containing ligands and Glu761 plays a similar role to that of Glu215. The carboxyphosphate and carbamoyl phosphate synthetic components, while topologically equivalent, are structurally different, as would be expected in light of their separate biochemical functions.
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  • 50
    ISSN: 1399-0047
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: The crystal structure of bovine heart cytochrome c oxidase has been determined at 2.8 Å resolution by the multiple isomorphous replacement (MIR) method with three heavy-atom derivatives. An asymmetric unit of the crystal has a molecular weight of 422 kDa. Eight heavy atoms as main sites of a CH3HgCl derivative were clearly located by solving the difference Patterson function. The electron density obtained by the MIR method was refined by density modification, consisting of solvent flattening, histogram matching and non-crystallographic symmetry averaging. The enzyme exhibits a dimeric structure in the crystal. Out of 3606 amino-acid residues in 26 subunits in the dimer, 3560 residues were located in the electron-density map. The structure was refined by X-PLOR. The final R factor and the free R factor were 0.199 and 0.252 at 2.8 Å resolution, respectively. One monomer in the dimeric structure with a stronger packing interaction has a lower averaged temperature factor than the other, by 16 Å2. The region \pm12 Å from the centre of the transmembrane part is almost 100% \alpha-helix, despite the glycine residue content being as high as 7.1% in the transmembrane region. The residues around haem a of animals have evolved away from those of bacteria in contrast with the residues of the haem a3. The hierarchy of the structural organization of the enzyme complex has been proposed on the basis of intersubunit interactions.
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  • 51
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    Acta crystallographica 55 (1999), S. 46-50 
    ISSN: 1399-0047
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: The X-ray structure of recombinant bovine pancreatic phospholipase A2 (PLA2), which specifically catalyzes the cleavage of the sn-2 acylester bond of phospholipids, has been refined at 1.5 Å resolution. The crystal belongs to the space group P212121 with unit-cell parameters a = 47.12, b = 64.59 and c = 38.14 Å similar to the native enzyme reported previously by Dijkstra et al. [J. Mol. Biol. (1981), 147, 97–123]. The refinement converged to an R value of 18.4% (Rfree = 22.8%) for 16 374 reflections between 10.0 and 1.5 Å resolution. The surface-loop residues (60–70) are ordered in the present orthorhombic recombinant enzyme, but disordered in the trigonal recombinant enzyme. The active-site residues, His48, Asp99, and the catalytic water superimpose well with the trigonal form. Besides the catalytic water which is hydrogen bonded to His48, it is often seen that there is a second water attached to the same N atom of His48 and simultaneously hydrogen bonded to the O atom of Asp49. It is thought that the second water facilitates the tautomerism of His48 for enzyme catalysis. The catalytic water is also hydrogen bonded to the equatorial water coordinated to the calcium ion. In addition to the equatorial water, there is also an axial calcium water and the additional structural water. These five common water molecules are hydrogen bonded to the additional 16 water molecules in the present orthorhombic structure which may further enhance the structural integrity of the active site. Besides the protein and one calcium ion, a total of 134 water molecules were located in the present high-resolution refinement.
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  • 52
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    Acta crystallographica 55 (1999), S. 60-66 
    ISSN: 1399-0047
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Two complexes between rainbow trout lysozyme (RBTL) and 4-methylumbelliferyl chitobioside, 4MeU-(GlcNAc)2, and chitotrioside, 4MeU-(GlcNAc)3, were produced by co-crystallization and soaking, respectively, and the crystal structures were solved at 2.0 Å resolution. The results show that 4-MeU-(GlcNAc)3 binds in subsites A–D and that 4-MeU-(GlcNAc)2 binds in subsites B–D in the active-site cleft of RBTL. This agrees well with earlier crystallographic studies on the binding of oligosaccharides of chitin to RBTL, which showed that (GlcNAc)3 binds to sites B–D in RBTL and not to A–C as seen in the human and turkey egg-white lysozymes. For both complexes the 4-MeU moiety in site D has diffuse electron density and is flexible, as it is only bound to water molecules and not to the protein. Since no electron density was observed in site E, the solved structures give views of nonproductive enzyme–substrate complexes.
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  • 53
    ISSN: 1399-0047
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: The α-toxin of Clostridium perfringens is the major virulence determinant for gas gangrene in man. The gene encoding the α-toxin has been cloned into E. coli from two strains of the bacterium (NCTC8237 and CER89L43) and subsequently purified to homogeneity. The two strains of α-toxin differ by five amino acids, resulting in the toxin from NCTC8237 being sensitive to chymotrypsin digestion while that from CER89L43 is resistant. The α-toxin from each of these strains has been crystallized in two different forms by the hanging-drop vapour-diffusion method at 293 K. CER89L43 form I crystals belong to space group R32 and have two molecules in the crystallographic asymmetric unit and a unit cell with a = b = 151.4, c = 195.5 Å, α = β = 90, γ = 120°. The crystals diffracted to dmin = 1.90 Å. The characteristics of the NCTC8237 form I crystals have already been reported. The form II crystals from both strains belong to space group C2221 with one molecule in the crystallographic asymmetric unit and, for strain CER89L43, have cell dimensions a = 61.05, b = 177.50, c = 79.05 Å, α = β = γ = 90°, while for strain NCTC8237 the cell dimensions are a = 60.50, b = 175.70, c = 80.20 Å, α = β = γ = 90°. The crystals diffracted to maximum resolutions of 1.85 and 2.1 Å for the CER89L43 and the NCTC8237 strains, respectively.
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  • 54
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    Acta crystallographica 55 (1999), S. 67-76 
    ISSN: 1399-0047
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: A multiple-wavelength anomalous diffraction (MAD) experiment was performed on an iridium derivative of hen egg-white lysozyme. Diffraction data were measured at five wavelengths on the X31 EMBL beamline on the DORIS III storage ring and at two further wavelengths on the X11 beamline. Four iridium-binding sites were located from the dispersive anomalous differences between two wavelengths at the rising and falling inflection points of the Ir LIII-edge white line using direct methods. All other attempts to determine the heavy-atom positions failed. The results demonstrate an experimental method whereby systematic error in MAD data due to sample absorption can be reduced where a white line is present in the absorption spectrum of a heavy atom.
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  • 55
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    Acta crystallographica 54 (1998), S. 1412-1413 
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    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Chitinase is necessary for fungal growth and cell division and, therefore, is an ideal target for the design of inhibitors which may act as antifungal agents. A chitinase from the fungal pathogen Coccidioides immitis has been expressed as a fusion protein with gluathione-S-transferase (GST), which aids in purification. After cleavage from GST, chitinase was crystallized from 30% PEG 4000 in 0.1 M sodium acetate pH 4.6. The crystals have a tetragonal crystal lattice and belong to space group P41212 or P43212 and diffract to 2.2 Å resolution. The unit-cell parameters are a = b = 91.2, c = 95.4 Å; there is only one chitinase molecule in the asymmetric unit.
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  • 56
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    Notes: Recombinant triosephosphate isomerase (TIM) from a hyperthermophilic Archaeon, Pyrococcus woesei, has been crystallized. Three crystal forms have been obtained: monoclinic, orthorhombic and hexagonal. The monoclinic crystals belong to space group P21 with cell dimensions a = 79.1, b = 89.2, c = 145.4 Å and β = 92.8°, and diffract to at least 2.6 Å. The orthorhombic crystals belong to space group P21212 with a = 89.4, b = 155.9, c = 79.5 Å, and diffract to 2.9 Å. Diffraction from the hexagonal form showed extensive disorder. The monoclinic form contains two tetramers in the asymmetric unit, which are in the same orientation but related by a pseudo-centring. The orthorhombic form contains one tetramer in the asymmetric unit which is in approximately the same orientation as in the monoclinic form. Knowledge of the structure of this hyperthermostable TIM, which is tetrameric in contrast to dimeric forms previously observed, will add to the understanding of protein thermostability.
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  • 57
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    Acta crystallographica 54 (1998), S. 1429-1431 
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    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Polyamine oxidase catalyses the oxidation of the secondary amino group of spermine, spermidine and their acetyl derivatives. The enzyme plays an important role in the regulation of polyamine intracellular concentration and is a member of the family of flavin-containing amine oxidases. Crystals of maize polyamine oxidase have been grown by the hanging-drop vapour-diffusion technique. The crystals are in hexagonal space group P6122 (or P6522) with cell dimensions a = b = 184.6, c = 280.9 Å. A native data set has been collected to 2.7 Å resolution at a synchrotron radiation source.
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  • 58
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    Acta crystallographica 54 (1998), S. 1435-1436 
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    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Two forms of the archaeal intron-encoded site-specific endonuclease I-DmoI, namely I-DmoIc and I-DmoIl, have been purified and crystallized. Crystals of I-DmoIc are rod-shaped and diffract to 3.0 Å resolution, but further analysis was hampered by twinning. Crystals of I-DmoIl, which is a six-amino-acid C-terminal truncation of I-DmoIc, are plate shaped and belong to space group C2 with cell parameters a = 93.72, b = 37.03, c = 55.56 Å, β = 113.4°, with one molecule per asymmetric unit (Vm = 2.01 Å3 Da−1). The crystals diffract to at least 2.3 Å resolution. A complete native data set has been measured and structure determination is on-going.
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  • 59
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    Notes: The phospholipases A2 (PLA2, E.C. 3.1.1.4, phosphatide sn2 acylhydrolases) are the major components of the venom of several snakes. They are responsible for several important pharmacological effects observed in ophidian incidents. PLA2 piratoxin II from Bothrops pirajai has been crystallized by the vapour-diffusion technique. X-ray diffraction data have been collected to 2.04 Å resolution (90.2% complete, Rmerge = 0.070). The space group is P21 and the cell parameters are a = 46.19, b = 60.36, c = 58.74 Å and β = 96.05°. The structure has been solved by molecular replacement using the crystallographic structure of PLA2 from Bothrops asper (PDB code 1CLP) as a search model.
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  • 60
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    Notes: The seed lectin DBL and the related stem and leaves lectin DB58 of the tropical legume Dolichos biflorus were crystallized, as well as complexes of DBL with adenine and with GalNAc(α1-3)[Fuc(α1-2)]Gal. The different crystal forms of DBL diffract to about 2.8 Å, while DB58 crystals diffract to 3.3 Å.
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  • 61
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    Acta crystallographica 54 (1998), S. 1453-1455 
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    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: GerE is the latest-acting of a series of factors which regulate gene expression in the mother cell during sporulation in Bacillus. The gene encoding GerE has been cloned from B. subtilis and overexpressed in Escherichia coli. Purified GerE has been crystallized by the hanging-drop vapour-diffusion method using polyethylene glycol as a precipitant. The small plate-like crystals belong to the monoclinic space group C2 and diffract beyond 2.2 Å resolution with a synchrotron radiation X-ray source.
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  • 62
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    Acta crystallographica 54 (1998), S. 1460-1463 
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    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: PhoB is the response regulator of the E. coli two-component signal transduction system for phosphate regulation. It is a transcription factor that activates more than 30 genes of the pho regulon. Crystals of the receiver domain of PhoB were obtained by applying the hanging-drop vapour-diffusion method. X-ray diffraction data have been collected using synchrotron radiation to 1.88 Å resolution. The crystals belong to the orthorhombic space group P212121 with unit-cell constants a = 34.11, b = 60.42, c = 119.97 Å. The Matthews parameter suggests that PhoB crystallizes with two molecules per asymmetric unit, suggesting that activating dimerization occurs in the crystal.
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  • 63
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    Acta crystallographica 55 (1999), S. 279-280 
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    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Hexitol nucleic acids are oligonucleotides built up from natural nucleobases and a phosphorylated 1,5-anhydrohexitol backbone. The anhydrohexitol oligonucleotide h(GTGTACAC) was synthesized using phosphoramidite chemistry and standard protecting groups. Crystals of h(GTGTACAC) were obtained at either 279 or 289 K by the hanging-drop vapour-diffusion technique using a 24-matrix screen for nucleic acid fragments. The crystals diffract beyond 2.0 Å resolution and belong to the hexagonal space group P6222 (or P6422) with unit-cell parameters a = 36.42 and c = 63.33 Å.
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  • 64
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    Acta crystallographica 55 (1999), S. 285-286 
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    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: The ATP-binding protein, MalK, of the bacterial ABC (ATP-binding-cassette) transport complex MalFGK2 provides the energy for the translocation of maltose and maltodextrins across the cytoplasmic membrane. The MalK protein from Salmonella typhimurium was overexpressed in Escherichia coli and crystallized by the hanging-drop method using (NH4)2SO4 as a precipitant. The crystals belong to space group P6x22 (most probably x = 1 or 5) with cell dimensions a = 181.8 and c = 182.5 Å, corresponding to three or four molecules per asymmetric unit. They diffract to a resolution of about 3 Å on a synchrotron X-ray source and are suitable for structure determination.
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  • 65
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    Acta crystallographica 55 (1999), S. 287-290 
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    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Pyrimidine nucleoside phosphorylase (PYNP) from B. stearothermophilus has been cloned and purified for crystallization. Crystals of a potential protein–inhibitor complex have been prepared by co-crystallization techniques using the substrate analog pseudouridine. These crystals provide good-quality diffraction images to 2.7 Å and belong to space group P21. The asymmetric unit contains the dimer structure of PYNP with unit-cell parameters a = 53.9, b = 71.9, c = 123.3 Å and β = 96.9°.
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  • 66
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    Acta crystallographica 55 (1999), S. 291-293 
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    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: YPD1 is a yeast osmoregulatory protein that functions in a phosphorelay signal-transduction pathway. YPD1 has been expressed in Escherichia coli, purified to homogeneity and crystallized. The crystals were obtained by hanging-drop vapor-diffusion using PEG 4000 as a precipitant. Preliminary X-ray diffraction analysis indicates that the crystals belong to tetragonal space group P43212 or P41212 with unit-cell dimensions a = b = 52.71, c = 244.02 Å. X-ray data to 2.7 and 3.0 Å have been collected from native crystals and a heavy-atom derivative, respectively. Positions for two Hg atoms have been located by analysis of difference Patterson maps.
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  • 67
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    Acta crystallographica 55 (1999), S. 281-284 
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    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: The genomic RNA of all retroviruses is encapsidated in virions as a dimer of single-stranded chains held together near their 5′-end. For HIV-1, the initial site of dimerization has been shown to be a hairpin with a nine-residue loop containing a self-complementary sequence of six residues. This structure is proposed to promote dimerization by loop–loop interaction and formation of a so-called `kissing complex'. A 23-nucleotide RNA strand containing the loop enclosed by a seven base-pair stem has been synthesized. This oligomer was crystallized by the vapour-diffusion method at 310 K, pH 6.5, with methyl-pentanediol as the precipitant agent in the presence of MgCl2, KCl and spermine. Quasi-complete diffraction data were obtained at 2.7 Å resolution with a conventional X-ray source and at 2.3 Å resolution on a synchrotron beamline. The space group is P3121 or its enantiomorph P3221, with cell parameters a = b = 60.1, c = 65.9 Å at ambient temperature, or a = b = 59.0, c = 64.3 Å in a nitrogen-gas stream. There are two oligomers per asymmetric unit as determined from absorbance measurements of a dissolved crystal whose volume was carefully determined. In some cases, either perfectly or partially twinned crystals were obtained. Perfect twinning is detected by an apparent hexagonal symmetry and yields unusable crystallographic data, whilst partial twinning yields usable data after adequate processing. Structure solution is under way by searching for heavy-atom derivatives and systematically substituting bromo- or iodo-uridines for uridines.
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  • 68
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    Acta crystallographica 55 (1999), S. 294-296 
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    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: A highly thermostable xylose isomerase from Thermus caldophilus has been expressed in Escherichia coli. The purified enzyme has an optimum temperature of 363 K. It has been crystallized at room temperature using ammonium sulfate as a precipitant. The crystal belongs to the orthorhombic space group P212121, with unit-cell parameters a = 84.35, b = 123.60, c = 140.24 Å. The presence of one molecule of tetrameric xylose isomerase in the asymmetric unit gives a crystal volume per protein mass (Vm) of 2.1 Å3 Da−1 and a solvent content of 41% by volume. The crystals initially showed diffraction to 1.7 Å Bragg spacing with synchrotron X-rays, and a set of native data extending to 2.3 Å resolution has been collected.
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  • 69
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    Notes: Until now, wild-type bacteriophage λ lysozyme had been impossible to crystallize. This difficulty could be overcome by the replacement of the four tryptophan residues by aza-tryptophans. Analysis of the intermolecular and intramolecular contacts in this modification allows understanding of the differences in behaviour between the native and modified molecules. Furthermore, this mutation was very useful for the creation of new heavy-atom binding sites and for the solution of the non-crystallographic symmetry, which is extremely important for phase improvement. This procedure seems to be generally applicable, at least in the search for new possibilities for heavy-atom binding sites.
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  • 70
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    Acta crystallographica 55 (1999), S. 436-442 
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    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Re-examination of the known data on crystalline forms of polyglycine reveals that the crystal modification `polyglycine I' has two different three-dimensional structures depending on the molecular weight. Structural models for both low molecular weight (LMW) and high molecular weight (HMW) polyglycine I crystals are described. In the LMW crystal model, the molecules have an unusual extended conformation generated by alternation of two mirror-symmetrical residual conformations along the chain. The molecules are parallel and each chain forms interpeptide hydrogen bonds with four adjacent chains. The structural model for the HMW crystal represents a composition of twinning crystallites. The crystallites themselves consist of antiparallel enantiomorphous chains united by hydrogen bonds to form rippled sheets. Calculations of the diffraction patterns and packing energy show that these polyglycine I structures have a higher level of conformity with the experimental data than previously suggested models. New insight into the structure of the polyglycine associates opens up the possibility of designing improved silk-like and nylon materials.
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  • 71
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    Acta crystallographica 55 (1999), S. 443-447 
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    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Crystal structures of the active-site mutants D99A and H48Q and the calcium-loop mutant D49E of bovine phospholipase A2 have been determined at around 1.9 Å resolution. The D99A mutant is isomorphous to the orthorhombic recombinant enzyme, space group P212121. The H48Q and the calcium-loop mutant D49E are isomorphous to the trigonal recombinant enzyme, space group P3121. The two active-site mutants show no major structural perturbations. The structural water is absent in D99A and, therefore, the hydrogen-bonding scheme is changed. In H48Q, the catalytic water is present and hydrogen bonded to Gln48 N, but the second water found in native His48 is absent. In the calcium-loop mutant D49E, the two water molecules forming the pentagonal bipyramid around calcium are absent and only one O atom of the Glu49 carboxylate group is coordinated to calcium, resulting in only four ligands.
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  • 72
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    Acta crystallographica 55 (1999), S. 448-457 
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    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: The investigation of the structure of the four conformers of the nonapeptide described here has an additional purpose: to illustrate a method for combining isomorphous replacement information with anomalous dispersion information within the linear equations that have found use in the analysis of multiple-wavelength anomalous dispersion data. In the present application, isomorphous replacement data were obtained from the replacement of naturally occurring S atoms in the nonapeptide with Se atoms. Only one wavelength was used for the analysis: Cu Kα radiation. Details of the analysis are presented, as well as the structural results obtained. It was found that the four independent molecules in the structure have similar, but not identical, conformations. The backbones fold into predominantly α-helices with one or two 310-type hydrogen bonds and have extended side chains. Three to four water molecules are associated with each of the four head-to-tail regions between the peptides. Optimal packing between hydrophobic surfaces may account for the existence of four molecules in an asymmetric unit.
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  • 73
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    Acta crystallographica 55 (1999), S. 458-463 
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    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: An algorithm is described which utilizes the solvent mask generated by the solvent-flattening technique to calculate a monomer molecular envelope. In the case where non-crystallographic symmetry (NCS) is present in the crystal and self-rotation angles are known from a self-rotation function, the resultant monomer envelopes can be used to search for the translation component of the NCS element by a three-dimensional search in real space. In the absence of self-rotation angles, the monomer envelope may be used to derive the NCS operators by reciprocal-space techniques. Thus, an automatic procedure for averaging directly from the solvent-flattening stage can be implemented. The procedure was instrumental in the structure solution of fibrinogen fragment D, which is presented as an example.
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    Acta crystallographica 55 (1999), S. 464-468 
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    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Real-space targets and molecular-dynamics search protocols have been combined to improve the convergence of macromolecular atomic refinement. This was accomplished by providing a local real-space target function for the molecular-dynamics program X-PLOR. With poor isomorphous replacement experimental phases, molecular dynamics does not improve real-space refinement. However, with high-quality anomalous diffraction phases convergence is improved at the start of refinement, and torsion-angle real-space molecular dynamics performs better than other available least-squares or maximum-likelihood methods in real or reciprocal space. It is shown that the improvements result from an optimization method that can escape local minima and from a reduction of overfitting through the implicit use of phases and through use of a local refinement in which errors in remote parts of the structure cannot be mutually compensating.
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    Acta crystallographica 55 (1999), S. 473-478 
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    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Mean standard errors in atomic displacement parameters (ADPs) resulting from protein crystal structure determinations are estimated by comparing the ADPs of protein-chain pairs of identical sequence within the same crystal or within different crystals displaying the same or different space groups. The estimated ADP standard errors increase nearly linearly as the resolution decreases – an unexpected result given the nonlinear dependence of the resolution on the amount of diffraction data. The estimated ADP standard errors are larger for side-chain and solvent-exposed atoms than for main-chain and buried atoms and, surprisingly, are also larger for residues in the helical secondary structure relative to other local backbone conformations. The results allow an estimate of the influence of crystallographic refinement restraints on ADP standard errors. Such corrections should be applied when comparing different protein structures.
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    Acta crystallographica 55 (1999), S. 469-472 
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    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: A procedure, called PBR (phase-bias reduction), has been developed to properly refine heavy-atom derivatives and to generate less biased heavy-atom phases when these derivatives contain common heavy-atom sites. Two independent events are obtained by splitting the refinement and phasing calculations into two stages, the first in which one of the derivatives having common sites is used together with the native amplitudes and the second in which both derivatives with common sites are used simultaneously, with one of them being used as the native data set. Improved centroid phases and the corresponding figures of merit are obtained by phase combination. This procedure has been used in the structure determination of the iron-cluster-containing protein pyruvate–ferredoxin oxidoreductase. When the common heavy-atom sites are properly treated by the PBR procedure, the resulting calculated centroid phases are improved with respect to classical heavy-atom refinement centroid phases where all derivatives are refined together. This leads to improved electron-density distributions, since anomalous difference Fourier maps calculated with the PBR-refined centroid phases and corresponding figures of merit show more clearly the positions of the iron sites.
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    Acta crystallographica 54 (1998), S. 1295-1305 
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    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: The structure of Nudaurelia capensis ω virus (NωV), a single-stranded RNA virus, was determined to 2.8 Å resolution. Triclinic crystals (a = 413.6, b = 410.2, c = 419.7 Å, α = 59.13, β = 58.9, γ = 64.0°) diffracted X-rays beyond 2.7 Å resolution. The unit cell contained one icosahedral virus particle, providing 60-fold non-crystallographic symmetry (n.c.s.) and structural redundancy. The particle orientation in the unit cell was determined by self-rotation function analyses. Initial phases to 18 Å resolution were derived from a hollow spherical model of 192 Å outer radius and 139 Å inner radius, filled with uniform electron density. Radii of the model were determined by maximizing the correlation of the model-based calculated data with the low-resolution X-ray diffraction and solution-scattering data. Phases were refined by 60-fold non-crystallographic electron-density averaging and extended in small steps to a resolution of 5 Å. The phases obtained represented a mixture of four different phase sets, each consistent with the icosahedral symmetry constraints. The resulting electron density was not interpretable. A difference Fourier map computed with the native and an isomorphous heavy-atom derivative data sets and phases refined by real-space averaging was interpretable only if data within the 10 Å resolution shell were used. Maps calculated with data significantly higher than 10 Å resolution failed to display a constellation of heavy-atom sites consistent with the T = 4 icosahedral symmetry. Attempts to extend the phases beyond 10 Å resolution, starting with either phases based on a model or single isomorphous replacement, were unsuccessful. Successful phase extension was achieved by computing the phases for the higher resolution reflections from a partial atomic model (poly gly) built into the averaged 10 Å electron-density map. Phases from this model served as the starting point for n.c.s. phase refinement and extension to slightly higher resolution. The atomic model was improved at each extension interval and these phases were used for the subsequent phase calculation and extension. The entire polypeptide backbone corresponding to the NωV structure was built into the map at 4 Å. The same procedure for phase refinement was used to extend the phases to 2.8 Å in small increments of resolution. The overall molecular averaging R factor and correlation coefficient at 2.8 Å resolution were 18.4% and 0.87, respectively.
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    Acta crystallographica 55 (1999), S. 149-156 
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    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Aspartyl-tRNA synthetase (AspRS) extracted from yeast is heterogeneous owing to proteolysis of its positively charged N-terminus; its crystals are of poor quality. To overcome this drawback, a rational strategy was developed to grow crystals of sufficient quality for structure determination. The strategy is based on improvement of the protein homogeneity and optimization of crystallization, taking advantage of predictions from crystal-growth theories. An active mutant lacking the first 70 residues was produced and initial crystallization conditions searched. The shape and habit of initial crystals were improved by establishing a phase diagram of protein versus crystallizing-agent concentrations. Growth of large well faceted crystals takes place at low supersaturations near the isochronic supersolubility curve. Further refinement led to reproducible growth of two crystalline forms of bipyramidal (I) or prismatic (II) habit. Both diffract X-rays better than crystals previously obtained with native AspRS. Complete data sets were collected at 3 Å resolution for form I (space group P41212) and form II (space group P3221) and molecular-replacement solutions were found in both space groups.
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    Acta crystallographica 55 (1999), S. 168-172 
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    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: The direct-methods program MULTAN88 has been applied to a known protein, ribonuclease (RNAP1), containing 808 non-H atoms, including five S atoms, plus 83 ordered solvent water molecules. Phase sets with mean phase errors between 69 and 75° were selected by modified figures of merit for trials with the full data at 1.17 Å resolution and also with restricted data at 1.25 and 1.5 Å resolution. These figures of merit had previously only been applied to protein structures containing heavy atoms, and this is the first demonstration of their usefulness with no heavy atom present. An initial set of 1091 phases from a 1.17 Å trial was developed by an objective procedure to give the full structure with a residual of 0.21, which agrees well with the published structure.
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    Acta crystallographica 55 (1999), S. 157-167 
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    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: A previous article [Fourme et al. (1995). J. Synchrotron Rad. 2, 36–48] presented the theoretical foundations of MASC, a new contrast-variation method using multiwavelength anomalous scattering, and reported the first experimental results. New experiments have been conducted both at the ESRF (Grenoble, France) and at LURE-DCI (Orsay, France), using cryocooled crystals of three proteins of known structures and very different molecular weights. Amplitudes of \{\Gamma_T({\bf h})\}, the `normal' structure factors of the anomalously scattering part of the crystal including the solvent zone and the ordered anomalous scattering sites (if any), have been extracted from multiwavelength data. In the very low resolution range (d \ge 20 Å), the agreement between experimental \{|\Gamma_T({\bf h})|\} and model values calculated from the bulk solvent is all the more satisfactory since the molecular weight of the protein is high. For spacings between 10 and 20 Å, the agreement between experimental \{|\Gamma_T({\bf h})|\} and model values is also satisfactory if one takes into account ordered anomalous scatterer sites. Such sites have been found in the three cases.
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  • 81
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    Copenhagen : International Union of Crystallography (IUCr)
    Acta crystallographica 55 (1999), S. 386-398 
    ISSN: 1399-0047
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: The structure of Bacillus amyloliquefaciens ribonuclease (barnase), an extracellular 110-residue enzyme initially solved at 2.0 Å resolution, has been refined at 1.5 Å using synchrotron radiation and an imaging-plate scanner. Refinement with anisotropic atomic displacement parameters resulted in increased accuracy of the structure. The final model has a crystallographic R factor of 11.5% and an Rfree of 17.4%. The three independent molecules in the asymmetric unit, referred to as A, B and C, allowed detailed analysis of this final model and meaningful comparison with structures of barnase complexed either with nucleotide inhibitors or with its natural intracellular inhibitor, barstar. The analysis of the overall solvent structure revealed a similar number of water molecules associated with each barnase molecule; among these were 16 equivalent buried solvent molecules, the locations of which are discussed in detail and classified on the basis of their structural role. The importance of the water molecules' contribution to the barnase–barstar interaction is also highlighted. The high accuracy of the present analysis revealed the presence of a Zn2+ ion mediating the contacts between pairs of symmetry-related A, B or C molecules; such an ion had previously only been identified for pairs of C molecules.
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  • 82
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    Copenhagen : International Union of Crystallography (IUCr)
    Acta crystallographica 55 (1999), S. 403-407 
    ISSN: 1399-0047
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Human lactoferrin (hLf) has considerable potential as a therapeutic agent. Overexpression of hLf in the fungus Aspergillus awamori has resulted in the availability of very large quantities of this protein. Here, the three-dimensional structure of the recombinant hLf has been determined by X-ray crystallography at a resolution of 2.2 Å. The final model, comprising 5339 protein atoms (residues 1–691, 294 solvent molecules, two Fe3+and two CO_3^{2-} ions), gives an R factor of 0.181 (free R = 0.274) after refinement against 32231 reflections in the resolution range 10–2.2 Å. Superposition of the recombinant hLf structure onto the native milk hLf structure shows a very high level of correspondence; the main-chain atoms for the entire polypeptide can be superimposed with an r.m.s. deviation of only 0.3 Å and there are no significant differences in side-chain conformations or in the iron-binding sites. Dynamic properties, as measured by B-value distributions or iron-release kinetics, also agree closely. This shows that the structure of the protein is not affected by the mode of expression, the use of strain-improvement procedures or the changes in glycosylation due to the fungal system.
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  • 83
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    Copenhagen : International Union of Crystallography (IUCr)
    Acta crystallographica 55 (1999), S. 414-421 
    ISSN: 1399-0047
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: The crystal structure of the `blue' copper protein plastocyanin from the cyanobacterium Phormidium laminosum has been solved and refined using 2.8 Å X-ray data. P. laminosum plastocyanin crystallizes in space group P43212 with unit-cell dimensions a = 86.57, c = 91.47 Å and with three protein molecules per asymmetric unit. The final residual R is 19.9%. The structure was solved using molecular replacement with a search model based on the crystal structure of a close homologue, Anabaena variabilis plastocyanin (66% sequence identity). The molecule of P. laminosum plastocyanin has 105 amino-acid residues. The single Cu atom is coordinated by the same residues – two histidines, a cysteine and a methionine – as in other plastocyanins. In the crystal structure, the three molecules of the asymmetric unit are related by a non-crystallographic threefold axis. A Zn atom lies between each pair of neighbouring molecules in this ensemble, being coordinated by a surface histidine residue of one molecule and by two aspartates of the other.
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  • 84
    ISSN: 1399-0047
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: The Agrobacterium radiobacter CCRC 14924 N-carbamyl-D-amino-acid amidohydrolase, the enzyme used for production of D-amino acids, was overexpressed in Escherichia coli JM109. The expressed protein was crystallized by vapour diffusion using lithium sulfate as precipitant. It crystallizes in space group P21 with unit-cell parameters a = 69.8, b = 67.9 and c = 137.8 Å and β = 96.4°. There are four molecules per asymmetric unit. Crystals diffract to 2.8 Å resolution using a rotating-anode source at cryogenic (113 K) temperatures.
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  • 85
    ISSN: 1399-0047
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: ADP-L-glycero-D-mannoheptose 6-epimerase is a 240 kDa NAD-dependent nucleotide diphosphosugar epimerase from Escherichia coli K12 which catalyzes the interconversion of ADP-D-glycero-D-mannoheptose and ADP-L-glycero-D-mannoheptose. ADP-L-glycero-D-mannoheptose is a required intermediate for lipopolysaccharide inner-core and outer-membrane biosynthesis in several genera of pathogenic and non-pathogenic Gram-negative bacteria. ADP-L-glycero-D-mannoheptose 6-epimerase was overexpressed in E. coli and purified to apparent homogeneity by chromatographic methods. Three crystal forms of the epimerase were obtained by a hanging-drop vapor-diffusion method. A native data set for crystal form III was collected in-house on a Rigaku R-AXIS-IIC image plate at 3.0 Å resolution. The form III crystals belong to the monoclinic space group P21. The unit-cell parameters are a = 98.94, b = 110.53, c = 180.68 Å and β = 90.94°. Our recent results show that these crystals diffract to 2.0 Å resolution at the Cornell High Energy Synchrotron Source. The crystal probably contains six 40 kDa monomers per asymmetric unit, with a corresponding volume per protein mass (Vm) of 4.11 Å3 Da−1 and a solvent fraction of 70%.
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  • 86
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    Acta crystallographica 55 (1999), S. 801-809 
    ISSN: 1399-0047
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Protein HU is a ubiquitous prokaryotic protein which controls the architecture of genomic DNA. It binds DNA non-specifically and promotes the bending and supercoiling of the double helical structure. HU is involved in many DNA-associated cellular processes, including replication, transcription and the packaging of DNA into chromosome-like structures. Originally determined at medium resolution, the crystal structure of HU has now been refined at 2.0 Å resolution. The high-resolution structure shows that the dimeric molecule is essentially a compact platform for two flexible and basic arms which wrap around the DNA molecule. To maximize the protein's stability, non-secondary structural regions are reduced to a minimum, there is an extensive aromatic hydrophobic core and several salt bridges and hydrogen-bonded water molecules knit together crucial regions. Based on the original medium-resolution structure of HU, several proposals were made concerning the structural basis of HU's ability to bind, bend and supercoil DNA. Each of these proposals is fully supported by the high-resolution structure. Most notably, the surfaces of the molecule which appear to mediate protein–DNA and protein–protein interactions have the ideal shapes and physicochemical properties to perform these functions.
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  • 87
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    Acta crystallographica 55 (1999), S. 810-819 
    ISSN: 1399-0047
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: The molecular interactions in crystals of oligonucleotides in the B form have been analysed and in particular the end-to-end interactions. Phosphate–phosphate interactions in dodecamers are also reviewed. A strong influence of packing constraints on the average conformation of the double helix is found. There is a strong relationship between the space group, the end-to-end interactions and the average conformation of DNA. Dodecamers must have a B-form average conformation with 10 ± 0.1 base pairs per turn in order to crystallize in the P212121 and related space groups usually found. Decamers show a wider range of conformational variation, with 9.7–10.6 base pairs per turn, depending on the terminal sequence and the space group. The influence of the space group in decamers is quite striking and remains unexplained. Only small variations are allowed in each case. Thus, crystal packing is strongly related to the average DNA conformation in the crystals and deviations from the average are rather limited. The constraints imposed by the crystal lattice explain why the average twist of the DNA in solution (10.6 base pairs per turn) is seldom found in oligonucleotides crystallized in the B form.
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  • 88
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    Acta crystallographica 55 (1999), S. 820-825 
    ISSN: 1399-0047
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: The direct-methods program SAYTAN has been applied successfully to a known protein, rubredoxin, which contains 52 amino-acid residues including an FeS4 unit, a sulfate ion and 102 solvent water molecules. Starting with initially random phases, useful sets can be obtained from multiple trials and selected by figures of merit at different resolutions. Phase extension followed by weighted Fourier recycling reveals a recognizable structure of rubredoxin. The model is refined against 1 Å resolution data to an R factor of 14.5% using the program SHELXL93.
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  • 89
    ISSN: 1399-0047
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Recombinant human glucose 6-phosphate dehydrogenase (G6PD) has been crystallized and its structure solved by molecular replacement. Crystals of the natural mutant R459L grow under similar conditions in space groups P212121 and C2221 with eight or four 515-residue molecules in the asymmetric unit, respectively. A non-crystallographic 222 tetramer was found in the C2221 crystal form using a 4 Å resolution data set and a dimer of the large β + α domains of the Leuconostoc mesenteroides enzyme as a search model. This tetramer was the only successful search model for the P212121 crystal form using data to 3 Å. Crystals of the deletion mutant ΔG6PD grow in space group F222 with a monomer in the asymmetric unit; 2.5 Å resolution data have been collected. Comparison of the packing of tetramers in the three space groups suggests that the N-terminal tail of the enzyme prevents crystallization with exact 222 molecular symmetry.
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  • 90
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    Copenhagen : International Union of Crystallography (IUCr)
    Acta crystallographica 55 (1999), S. 243-246 
    ISSN: 1399-0047
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Solving the phase problem is the crucial and quite often the most difficult and time-consuming step in crystallographic structure determination. The traditional methods of isomorphous replacement (MIR or SIR) and molecular replacement require the availability of an isomorphous heavy-atom derivative or the structure of a homologous protein, respectively. Here, a method is presented which utilizes the low-resolution molecular shape determined from solution X-ray scattering data for the molecular search. The molecular shape of a protein is an important structural property and can be determined directly by the small-angle scattering technique. The idea of locating this molecular shape in the crystallographic unit cell has been tested with experimental diffraction data from nitrite reductase (NiR). The conventional Patterson search proved to be unsuccessful, as the intra-envelope vectors are uniformly distributed and do not match those of intra-molecular (atom-to-atom) vectors. A direct real-space search for orientation and translation was then performed. A self-rotation function using 2.8 Å crystallographic data yielded the polar angles of the non-crystallographic threefold axis. Knowledge of the orientation of this axis reduces the potential six-dimensional search to four (Eulerian angle γ and three translational parameters). The direct four-dimensional search within the unit cell produced a clear solution. The electron-density map based on this solution agrees well with the known structure, and the phase error calculated from the map was 61° within 20 Å resolution. It is anticipated that the low-resolution envelope can be used as a starting model for phase extension by the maximum-entropy and density-modification method.
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  • 91
    ISSN: 1399-0047
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: We have crystallized and performed preliminary X-ray characterization of the complex between the DNAase domain of the E9 colicin and its cognate immunity protein Im9. The dissociation constant for this complex, Kd = 1 × 10−16 M, reveals it to be one of the highest affinity protein–protein interactions known. Single crystals of the 1:1 complex were grown from microseeding experiments using PEG 4K as precipitant. The space group is P212121 with one molecule of complex in the asymmetric unit, and crystals contain approximately 43% solvent. These crystals are inherently non-isomorphous and so selenomethionine-derivatized protein has been prepared and crystals grown for MAD phasing experiments.
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  • 92
    ISSN: 1399-0047
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: A truncated soluble form of the murine class I major histocompatibility antigen complex H–2Dd was cloned using an Escherichia coli based system. It was expressed, refolded in vitro and crystallized in a complex with murine β2 microglobulin and the peptide RGPGRAFVTI from the V3-loop of the gp160 HIV-1 protein. Crystals belonging to the space group P212121 with cell dimensions a = 51.3, b = 92.5, c = 108.8 Å were obtained using two different crystallization conditions. The crystals contain one complex per asymmetric unit and diffract to at least 2.4 Å resolution.
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  • 93
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    Copenhagen : International Union of Crystallography (IUCr)
    Acta crystallographica 55 (1999), S. 263-265 
    ISSN: 1399-0047
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: During homologous recombination in Escherichia coli the RuvA, B and C proteins interact specifically with the Holliday junction formed by the action of RecA to promote the strand-exchange reaction. RuvA, a homotetrameric protein of molecular weight 88 kDa, has been overexpressed in E. coli, purified and co-crystallized with a synthetic Holliday junction substrate made from four 18-base deoxyoligonucleotides. Crystals were grown using the hanging-drop vapour-diffusion method with sodium acetate as the precipitant. The crystals diffract to a resolution of 6 Å and belong to the monoclinic system, space group C2, with cell parameters a = 148, b = 148, c = 106 Å and β = 123°. The X-ray analysis of these crystals should reveal the structure of the Holliday junction and its mode of binding to RuvA, providing new insights into the molecular mechanism of genetic recombination.
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  • 94
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    Copenhagen : International Union of Crystallography (IUCr)
    Acta crystallographica 55 (1999), S. 865-868 
    ISSN: 1399-0047
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: The etiologic agent of tuberculosis, Mycobacterium tuberculosis, has been shown to secrete the enzyme glutamine synthetase (TB-GS) which is apparently essential for infection. Four crystal forms of a recombinant TB-GS were grown. The one chosen for synchrotron X-ray data collection belongs to space group P212121 with unit-cell dimensions 208 × 258 × 274 Å, yielding 2.4 Å resolution data. A Matthews number of 2.89 Å3 Da−1 is found, corresponding to 24 subunits of molecular mass 1300 kDa in the asymmetric unit. From earlier work, the structure of Salmonella typhimurium GS, which is 51% identical in sequence to TB-GS, is known to be dodecameric with 622 symmetry. Self-rotation calculations on the TB-GS X-ray data reveal only one set of sixfold and twofold axes of symmetry. A Patterson map calculated from the native X-ray data confirms that there are two dodecamers in the asymmetric unit, having both their sixfold and twofold axes parallel to one another.
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  • 95
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    Copenhagen : International Union of Crystallography (IUCr)
    Acta crystallographica 55 (1999), S. 736-744 
    ISSN: 1399-0047
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: The structure of the FKBP12–rapamycin–FRB ternary complex has now been refined at 2.2 Å resolution. The cell-cycle arrest agent rapamycin binds FK506-binding protein (FKBP12) and the FKBP12–rapamycin binding (FRB) domain of FKBP12–rapamycin associated protein (FRAP) simultaneously, and the inhibition of FRAP is responsible for rapamycin's biological activity. The conformation of rapamycin in the ternary complex is very similar to that observed in the FKBP12–rapamycin binary complex, with an r.m.s. difference of only 0.30 Å. However, a slight (9°) rotation repositions the FRB-binding face of rapamycin in the ternary complex. There are extensive rapamycin–protein interactions and relatively few interactions between the two protein partners FKBP12 and FRB, these interactions mainly involving residues in the 40s and 80s loops of FKBP12 and α1 and α4 of FRB. The high-resolution refinement has revealed the crucial role of several buried waters in the formation of the ternary complex.
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  • 96
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    Acta crystallographica 55 (1999), S. 869-872 
    ISSN: 1399-0047
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: α-D-Glucuronidases cleave the α-1,2-glycosidic bond of the 4-O-methyl-α-D-glucuronic acid side chain in xylan. Of the xylan-debranching hydrolases, these enzymes are the least studied and characterized. The α-glucuronidase gene (aguA) from Bacillus stearothermophilus T-6 has been cloned, sequenced and overproduced in Escherichia coli. The gene encodes for a protein of 679 amino acids with a calculated molecular weight of 78480 and a pI of 5.42. α-Glucuronidase T-6 shows high homology to the α-glucuronidases of Thermotoga maritima (60% identity) and of Trichoderma reesei (44% identity). Based on the amino-acid sequence similarity, it is likely that these enzymes represent a new class of glycosyl hydrolases. Crystallographic studies of α-glucuronidase T-6 were initiated to study the mechanism of catalysis, as well as to provide a structural basis for rational introduction of enhanced thermostability by site-specific mutagenesis. In this report, the crystallization and preliminary crystallographic characterization of the native α-glucuronidase T-6 enzyme is described. Two crystal forms were found suitable for detailed crystal structure analysis. The T1 form was obtained by the vapour-diffusion method using PEG 4000 as a precipitant and 2-propanol as an organic additive. The crystals belong to a primitive tetragonal crystal system (space group P41212 or P43212) with unit-cell dimensions a = b = 76.1 and c = 331.2 Å. These crystals are mechanically strong, are stable in the X-ray beam and diffract X-rays to better than 2.4 Å resolution. A full 3.0 Å resolution diffraction data set (97.3% completeness, Rmerge 9.8%) has recently been collected on one crystal at room temperature using a rotating-anode X-ray source and an R-AXIS IIc imaging-plate detector. The M1 form was obtained and characterized by similar techniques. The best crystallization occurred at a slightly lower pH and a lower concentration of 2-propanol. The crystals belong to a primitive monoclinic crystal system (space group P21) with unit-cell dimensions a = 65.8, b = 127.4, c = 96.6 Å and β = 97.9°. These crystals are also quite strong and stable, and diffract to better than 2.8 Å resolution. A full 2.8 Å resolution diffraction data set (96.2% completeness, Rmerge 7.6%) has recently been collected on one crystal at room temperature using the same R-AXIS IIc setup. Both forms are currently being used to obtain crystallographic phasing via isomorphous heavy-atom derivatives and selenomethionine MAD experiments.
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  • 97
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    Acta crystallographica 55 (1999), S. 877-879 
    ISSN: 1399-0047
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Periplasmic nitrate reductase from the sulfate-reducing bacterium Desulfovibrio desulfuricans ATCC 27774 contains two molybdopterin guanine dinucleotide cofactors and one [4Fe–4S] cluster as prosthetic groups and catalyzes the conversion of nitrate to nitrite. Crystals of the oxidized form of this enzyme were obtained using PEG as precipitant and belong to space group P3121 or P3221, with unit-cell dimensions a = b = 106.3, c = 135.1 Å. There is one monomer of 80 kDa in the asymmetric unit, which corresponds to a Matthews ratio of 2.75 Å3 Da−1. Using cryo-cooling procedures and X-rays from a rotating-anode generator, diffraction was observed to beyond 3.0 Å resolution.
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  • 98
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    Acta crystallographica 55 (1999), S. 883-884 
    ISSN: 1399-0047
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Two orthorhombic forms of crystals of the haptoglobin–hemoglobin complex were obtained using polyethylene glycol as precipitant. These crystals did not diffract well enough for data collection and work on the complex is no longer continued. However, the description of the crystallization conditions may be useful in future endeavors to obtain suitable crystals.
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  • 99
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    Acta crystallographica 55 (1999), S. 542-543 
    ISSN: 1399-0047
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: The molybdenum-responsive ModE regulatory protein from Escherichia coli has been purified and used in crystallization trials. Two crystal forms have been observed. Form I is tetragonal, P41212 (or enantiomorph), with a = b = 72.3, c = 246.2 Å and diffracts to medium resolution. Form II is orthorhombic, P21212, with a = 82.8, b = 127.9, c = 64.0 Å and diffraction has been observed beyond 2.8 Å resolution. Structural analysis, in combination with ongoing biochemical characterization, will assist the elucidation of the structure–activity relationship in regulating the uptake of molybdate in bacteria.
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  • 100
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    Copenhagen : International Union of Crystallography (IUCr)
    Acta crystallographica 55 (1999), S. 544-546 
    ISSN: 1399-0047
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Crystals of 1,5-α-arabinanase A from Pseudomonas fluorescens subspecies cellulosa have been obtained by vapour diffusion. The crystals belong to the space group P6122 with unit-cell parameters a = b = 91.6, c = 179.4 Å with one molecule in the asymmetric unit. The native crystals and, to a much greater extent, heavy-atom soaked crystals are sensitive to radiation which necessitates cryocooling. Suitable cryocooling conditions have been established, though a shrinkage of the unit cell is observed, with a = b = 88.8 and c = 176.9 Å.
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