87 research outputs found

    Crystal structure of a murine α-class glutathione S-transferase involved in cellular defense against oxidative stress

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    Glutathione S-transferases (GSTs) are ubiquitous multifunctional enzymes which play a key role in cellular detoxification. The enzymes protect the cells against toxicants by conjugating them to glutathione. Recently, a novel subgroup of α-class GSTs has been identified with altered substrate specificity which is particularly important for cellular defense against oxidative stress. Here, we report the crystal structure of murine GSTA4-4, which is the first structure of a prototypical member of this subgroup. The structure was solved by molecular replacement and refined to 2.9 Å resolution. It resembles the structure of other members of the GST superfamily, but reveals a distinct substrate binding site.

    Preliminary X-ray crystallographic analysis of the secreted chorismate mutase from Mycobacterium tuberculosis: a tricky crystallization problem solved

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    A method is presented that allowed the diffraction limit of crystals of the secreted chorismate mutase from M. tuberculosis to be improved from approximately 3.5 to 1.3 Å. To obtain large well diffracting crystals, it was critical to initiate crystallization at higher precipitant concentration and then transfer the drops to lower precipitant concentrations within 5–15 min

    Coping with oxidative stress

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    Three-dimensional structure of endo-1,4-beta-xylanase I from Aspergillus niger:Molecular basis for its low pH optimum

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    The crystal structure of endo-1,4-β-xylanase I fromAspergillus nigerhas been solved by molecular replacement and was refined to 2.4 Å resolution. The finalR-factor for all data from 6 to 2.4 Å is 17.9%. TheA. nigerxylanase has a characteristic fold which is unique for family G xylanases (root-mean-square deviation=1.1 Å toTrichoderma reeseixylanase I, which has 53% sequence identity). It consists of a single domain composed predominantly of β-strands. Two β-sheets are twisted around a deep, long cleft, which is lined with many aromatic amino acid residues and is large enough to accommodate at least four xylose residues. The two conserved glutamate residues, Glu79 and Glu170, which are likely to be involved in catalysis, reach into this cleft from opposite sides.A. nigerxylanase I is of particular commercial interest because of its low pH optimum. A model is proposed which explains this low pH optimum compared to other members of xylanase family G
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