Structural investigation of the molybdenum site of the periplasmic nitrate reductase from Thiosphaera pantotropha by X-ray absorption spectroscopy

B Bennett, J M Charnock, H J Sears, B C Berks, A J Thomson, S J Ferguson, C D Garner, D J Richardson

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    16 Citations (Scopus)

    Abstract

    The molybdenum centre of the periplasmic respiratory nitrate reductase from the denitrifying bacterium Thiosphaera pantotropha has been probed using molybdenum K-edge X-ray absorption spectroscopy. The optimum fit of the Mo(VI) EXAFS suggests two ==O, three -S- and either a fourth -S- or an -O-/-N- as molybdenum ligands in the ferricyanide-oxidized enzyme. Three of the -S- ligands are proposed to be the two sulphur atoms of the molybdopterin dithiolene group and Cys-181. Comparison of the EXAFS of the ferricyanide-oxidized enzyme with that of a nitrate-treated sample containing 30% Mo(V) suggests that the Mo(VI)-->Mo(V) reduction is accompanied by conversion of one ==O to -O-. The best fit to the Mo(IV) EXAFS of dithionite-reduced enzyme was obtained using one ==O, one -O- and four -S-/-Cl ligands. The periplasmic nitrate reductase molybdenum co-ordination environment in both the Mo(VI) and Mo(IV) oxidation states is distinct from that found in the membrane-bound respiratory nitrate reductase.

    Original languageEnglish
    Pages (from-to)557-563
    Number of pages7
    JournalBiochemical Journal
    Volume317
    Issue number2
    DOIs
    Publication statusPublished - 15 Jul 1996

    Keywords

    • Amino Acid Sequence
    • Ferricyanides
    • Fourier Analysis
    • Gram-Negative Chemolithotrophic Bacteria
    • Ligands
    • Metalloproteins
    • Models, Chemical
    • Molecular Sequence Data
    • Molybdenum
    • Nitrate Reductase
    • Nitrate Reductases
    • Nitrates
    • Oxidation-Reduction
    • Sequence Homology, Amino Acid
    • Spectrum Analysis
    • X-Rays
    • Comparative Study
    • Journal Article
    • Research Support, Non-U.S. Gov't

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