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  • Crystal structure of Escherichia coli xanthine phosphoribosyltransferase

    Author(s)
    Vos, S
    deJersey, J
    Martin, JL
    Griffith University Author(s)
    Martin, Jennifer
    Year published
    1997
    Metadata
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    Abstract
    Xanthine phosphoribosyltransferase (XPRT; EC 2.4.2.22) from Escherichia coli is a tetrameric enzyme having 152 residues per subunit. XPRT catalyzes the transfer of the phosphoribosyl group from 5-phospho-α-d-ribosyl 1-pyrophosphate (PRib-PP) to the 6-oxopurine bases guanine, xanthine, and hypoxanthine to form GMP, XMP, and IMP, respectively. Crystals grown in the absence of substrate or product were used to determine the structure of XPRT at a resolution of 1.8 Å, by multiple isomorphous replacement. The core structure of XPRT includes a five-stranded parallel β-sheet surrounded by three α-helices, which is similar to that ...
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    Xanthine phosphoribosyltransferase (XPRT; EC 2.4.2.22) from Escherichia coli is a tetrameric enzyme having 152 residues per subunit. XPRT catalyzes the transfer of the phosphoribosyl group from 5-phospho-α-d-ribosyl 1-pyrophosphate (PRib-PP) to the 6-oxopurine bases guanine, xanthine, and hypoxanthine to form GMP, XMP, and IMP, respectively. Crystals grown in the absence of substrate or product were used to determine the structure of XPRT at a resolution of 1.8 Å, by multiple isomorphous replacement. The core structure of XPRT includes a five-stranded parallel β-sheet surrounded by three α-helices, which is similar to that observed in other known phosphoribosyltransferase (PRTase) structures. The XPRT structure also has several interesting features. A glutamine residue in the purine binding site may be responsible for the altered 6-oxopurine base specificity seen in this enzyme compared to other 6-oxopurine PRTases. Also, we observe both a magnesium ion and a sulfate ion bound at the PRib-PP binding site of XPRT. The sulfate ion interacts with Arg-37 which has a cis-peptide conformation, and the magnesium ion interacts with Asp-89, a highly conserved acidic residue in the PRib-PP binding site motif. The XPRT structure also incorporates a feature which has not been observed in other PRTase structures. The C-terminal 12 residues of XPRT adopt an unusual extended conformation and make interactions with a neighboring subunit. The very last residue, Arg-152, could form part of the active site of a symmetry-related subunit in the XPRT tetramer.
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    Journal Title
    Biochemistry
    Volume
    36
    Issue
    14
    DOI
    https://doi.org/10.1021/bi962640d
    Subject
    Medicinal and biomolecular chemistry
    Biochemistry and cell biology
    Biochemistry and cell biology not elsewhere classified
    Medical biochemistry and metabolomics
    Publication URI
    http://hdl.handle.net/10072/347904
    Collection
    • Journal articles

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