1nul | pdb_00001nul

XPRTASE FROM E. COLI

spinqualitylabelsall models 1nul, resolution 1.80Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image   Print3D Structural highlights 1nul is a 2 chain structure with sequence from Escherichia coli. Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance. Ligands: MG, SO4 Activity: Xanthine phosphoribosyltransferase, with EC number 2.4.2.22 Resources: FirstGlance, OCA, PDBe, RCSB, PDBsum, ProSAT Function [XGPT_ECOLI] Acts on guanine, xanthine and to a lesser extent hypoxanthine. Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMed 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-alpha-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 A, by multiple isomorphous replacement. The core structure of XPRT includes a five-stranded parallel beta-sheet surrounded by three alpha-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. Crystal structure of Escherichia coli xanthine phosphoribosyltransferase.,Vos S, de Jersey J, Martin JL Biochemistry. 1997 Apr 8;36(14):4125-34. PMID:9100006 From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See Also Phosphoribosyltransferase

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