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  • Articles  (3)
  • crystal structure
  • Springer  (3)
  • American Chemical Society
  • 1995-1999  (3)
  • Biology  (3)
  • 1
    Electronic Resource
    Electronic Resource
    Identification of proton transfer pathways in the X-ray crystal structure of the bacterial reaction center from Rhodobacter sphaeroides (1998)
    Springer
    Photosynthesis research 55 (1998), S. 119-125 
    Details
    ISSN: 1573-5079
    Keywords: bacterial photosynthesis ; crystal structure ; electron transfer ; proton transfer
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Structural features that have important implications for the fundamental process of transmembrane proton transfer are examined in the recently published high resolution atomic structures of the reaction center (RC) from Rhodobacter sphaeroides in the dark adapted state (DQAQB) and the charged separated state (D+QAQB −); the latter is the active state for proton transfer to the semiquinone. The structures have been determined at 2.2 Å and 2.6 Å resolution, respectively, as reported by Stowell et al. (1997) [Science 276: 812–816]. Three possible proton transfer pathways (P1, P2, P3) consisting of water molecules and/or protonatable residues were identified which connect the QB binding region with the cytoplasmic exposed surface at Asp H224 & Asp M240 (P1), Tyr M3 (P2) and Asp M17 (P3). All three represent possible pathways for proton transfer into the RC. P1 contains an uninterrupted chain of water molecules. This path could, in addition, facilitate the exchange of quinone for quinol during the photocycle by allowing water to move into and out of the binding pocket. Located near these pathways is a cluster of electrostatically interacting acid residues (Asp-L213, Glu-H173, Asp-M17, Asp H124, Asp-L210 and Asp H170) each being within 4.5 Å of a neighboring carboxylic acid or a bridging water molecule. This cluster could serve as an internal ‘proton reservoir’ facilitating fast protonation of QB − that could occur at a rate greater than that attainable by proton uptake from solution.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006047519260
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  • 2
    Electronic Resource
    Electronic Resource
    Cytochrome c Oxidase (Heme aa 3) from Paracoccus denitrificans: Analysis of Mutations in Putative Proton Channels of Subunit I (1998)
    Springer
    Journal of bioenergetics and biomembranes 30 (1998), S. 89-97 
    Details
    ISSN: 1573-6881
    Keywords: Terminal oxidase ; redox coupling ; electrochemical gradient ; electron transport ; energy transduction ; proton translocation ; crystal structure ; site-directed mutagenesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Physics
    Notes: Abstract One of the challenging features of energy-transducing terminal oxidases, like the aa 3 cytochrome c oxidase of Paracoccus denitrificans, is the translocation of protons across the cytoplasmic membrane, which is coupled to the transfer of electrons to oxygen. As a prerequisite for a more advanced examination of the enzymatic properties, several amino acid residues, selected on the basis of recent three-dimensional structure determinations, were exchanged in subunit I of the Paracoccus enzyme by site-directed mutagenesis. The properties of the mutated oxidases were analyzed by different methods to elucidate whether they are involved in the coupled and coordinated transfer of protons via two different pathways either to the site of oxygen reduction or through the enzyme from the cytoplasm to the periplasmic side.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1020515713103
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  • 3
    Electronic Resource
    Electronic Resource
    Recent advances in the structure and function of isopenicillin N synthase (1999)
    Springer
    Antonie van Leeuwenhoek 75 (1999), S. 33-39 
    Details
    ISSN: 1572-9699
    Keywords: active site ; crystal structure ; iron binding motif ; isopenicillin N synthase ; mechanism of action
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Isopenicillin N synthase is a key enzyme in the biosynthesis of penicillin and cephalosporin antibiotics, catalyzing the oxidative ring closure of δ-(L-α-aminoadipoyl)-L-cysteinyl-D-valine to form isopenicillin N. Recent advances in our understanding of the unique chemistry of this enzyme have come through the combined application of spectroscopic, molecular genetic and crystallographic approaches and led to important new insights into the structure and function of this enzyme. Here we review new information on the nature of the endogenous ligands that constitute the ferrous iron active site, sequence evidence for a novel structural motif involved in iron binding in this and related non-heme iron dependent dioxygenases, crystal structure studies on the enzyme and its substrate complex and the impact of these and site-directed mutagenesis studies for unraveling the mechanism of the isopenicillin N synthase reaction.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1001723202234
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