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  • 1
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    ISSN: 0887-3585
    Keywords: RNase H ; Mg2+-binding site ; catalytic mechanism ; molecular replacement ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: To obtain more precise insight into the Mg2+-binding site essential for RNase HI catalytic activity, we have determined the crystal structure of E. coli RNase HI in complex with Mg2+. The analyzed cocrystal, which is not isomorphous with the Mg2+-free crystal previously refined at 1.48 Å resolution, was grown at a high MgSO4 concentration more than 100 mM so that even weakly bound Mg2+ sites could be identified. The structure was solved by the molecular replacement method, using the Mg2+-free crystal structure as a search model, and was refined to give a final R-value of 0.190 for intensity data from 10 to 2.8 Å, using the XPLOR and PROLSQ programs. The backbone structures are in their entirety very similar to each other between the Mg2+-bound and the metal-free crystals, except for minor regions in the enzyme interface with the DNA/RNA hybrid. The active center clearly revealed a single Mg2+ atom located at a position almost identical to that previously found by the soaking method. Although the two metal-ion mechanism had been suggested by another group (Yang, W., Hendrickson, W.A., Crouch, R.J., Satow, Y. Science 249:1398-1405, 1990) and partially supported by the crystallographic study of inactive HIV-1 RT RNase H fragment (Davies, J.F., II, Hostomska, Z., Hostomsky, Z., Jordan, S.R., Matthews, D. Science 252:88-95, 1991), the present result excludes the possibility that RNase HI requires two metal-binding sites for activity. In contrast to the features in the metal-free enzyme, the side chains of Asn-44 and Glu-48 are found to form coordinate bonds with Mg2+ in the metal-bound crystal. © 1993 Wiley-Liss, Inc.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature structural & molecular biology 11 (2004), S. 632-636 
    ISSN: 1545-9985
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Medicine
    Notes: [Auszug] DNA polymerase requires two processing factors, sliding clamps and clamp loaders, to direct rapid and accurate duplication of genomic DNA. In eukaryotes, proliferating cell nuclear antigen (PCNA), the ring-shaped sliding clamp, encircles double-stranded DNA within its central hole and tethers the ...
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  • 3
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Biopolymers 10 (1971), S. 681-698 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Four fragments (named K, L, M, and N) of Escherichia coli formylmethionine transfer RNA have been prepared by a partial digestion with ribonuclease T1 followed by a chromatographic separation with a DEAE-Sphadex (A-25) column and then a DEAE-cellulose column. The fragment K is the anticodon fragment with 19 nucleotides (previously reported). L is a fragment with 57 nucleotides involving the 3′-terminal (CCA). M is a fragment with 51 nucleotides which is equal to L except that M lacks 6 nucleotides at the 3′-terminal. N is a fragment with 20 nucleotides which involved the 5′-terminal and corresponds to the complementary half to L. The infrared absorption spectrum has been observed of each of these fragments and two equimolar mixtures L + N and M + N in D2O solutions at several temperatures. The results indicate that at 37°C, K has about 4 hydrogen-bonded base-pairs, L about 11, and M about 13. On the other hand, fragment N is found to have only three weak G-C pairs. For both L + N and M + N, 15-17 strong base pairs are found. The observations give direct support to the clover-leaf structure and at the same time provide information on the stability of each of the four arms in the structure.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Biopolymers 12 (1973), S. 799-816 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Infrared and Raman spectra of aqueous poly(rA-rU)·poly(rA-rU), the double-helical complex containing strands of alternating riboadenylate and ribouridylate residues, display significant differences from one another and from corresponding spectra of poly(rA)·poly(rU), the double-helical complex of riboadenylate and ribouridylate homopolymers. Parallel studies on the copolymer and homopolymer complexes by cesium sulfate density gradient centrifugation, ultraviolet absorption spectroscopy, hydrogenion titration, 1-N oxidation of adenine residues by monoperphthalic acid and X-ray diffraction reveal, however, that the geometry of base pairing between adenine and uracil is closely similar in each complex and apparently of the Watson-Crick type. Therefore the differences observed between vibrational spectra of poly (rA-rU)·poly (rA-rU) and poly(rA)·poly(rU) are not due to different base-pairing schemes but may be attributed to differences in vibrational coupling between vertically stacked bases. Vibrational coupling may also account for the differences between infrared and Raman spectra of the same complex. Thus, the present results indicate that infrared and Raman frequencies of RNA in the region 1750-1550 cm-1 should be dependent on the base sequence.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    ISSN: 0887-3585
    Keywords: ribonuclease H ; Thermus thermophilus HB8 ; DNA/RNA hybrid ; crystallization ; X-ray crystallography ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Ribonuclease H from an extreme thermophile, Thermus thermophilus HB8, has been crystallized from solutions at low ionic strength. The crystals belong to the hexagonal space group P6 122 (or P6 522), with unit cell parameters a = b = 44.7 Å, c = 314.7 Å. They contain one 18,000 Mr molecule per asymmetric unit and diffract to 2.8 Å resolution. © 1993 Wiley-Liss, Inc.
    Additional Material: 2 Ill.
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  • 6
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    ISSN: 0887-3585
    Keywords: Tus ; terminus site ; protein-DNA interaction ; replication arrest ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Crystals of the Escherichia coli replication terminator protein (Tus) complexed with its binding site DNA were obtained by a microdialysis method using PEG 4000. They belong to the tetragonal space group P41212 or P43212 with the unit cell parameter: a = 68.1 Å, c = 230.7 Å and contain one protein-DNA complex in an asymmetric unit. The native data set has been collected to 2.7 Å resolution.
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  • 7
    Electronic Resource
    Electronic Resource
    [s.l.] : Macmillian Magazines Ltd.
    Nature 401 (1999), S. 713-717 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Granulocyte colony-stimulating factor (GCSF) is the principal growth factor regulating the maturation, proliferation and differentiation of the precursor cells of neutrophilic granulocytes and is used to treat neutropenia. GCSF is a member of the long-chain subtype of the class 1 cytokine ...
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  • 8
    Electronic Resource
    Electronic Resource
    [s.l.] : Macmillian Magazines Ltd.
    Nature 407 (2000), S. 971-977 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] The metabotropic glutamate receptors (mGluRs) are key receptors in the modulation of excitatory synaptic transmission in the central nervous system. Here we have determined three different crystal structures of the extracellular ligand-binding region of mGluR1—in a complex with glutamate ...
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  • 9
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 383 (1996), S. 598-603 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] The crystal structure of the Escherichia colireplication-terminator protein (Tus) bound to terminus-site (Ter) DNA has been determined at 2.7 Å resolution. The Tus protein folds into a previously undescribed architecture divided into two domains by a central basic cleft. This cleft ...
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  • 10
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 223 (1969), S. 537-538 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] The nonadecanucleotide fragment of formyl-methionine ZRNAf (£RNAfMet) from Escherichia coli, which contains the anticodon1 was obtained from a partial digest of the ZRNA with ribonuclease T\ by 'DEAE-Sephadex' column chromatography2. The "Fraction K"2 is almost pure (〉 90 per cent) ...
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