1NUL

XPRTASE FROM E. COLI

Summary for 1NUL

• Entry DOI: 10.2210/pdb1nul/pdb
• Descriptor: XANTHINE-GUANINE PHOSPHORIBOSYLTRANSFERASE, SULFATE ION, MAGNESIUM ION, ... (4 entities in total)
• Functional Keywords: phosphoribosyltransferase, transferase, purine salvage enzyme
• Biological source: Escherichia coli
• Cellular location: Cell inner membrane; Peripheral membrane protein (Probable): P0A9M5
• Total number of polymer chains: 2
• Total formula weight: 34223.87

Authors

Vos, S.,De Jersey, J.,Martin, J.L. (deposition date: 1996-10-15, release date: 1997-05-15, Last modification date: 2024-02-14)

Primary citation

Vos, S.,de Jersey, J.,Martin, J.L.
Crystal structure of Escherichia coli xanthine phosphoribosyltransferase.
Biochemistry, 36:4125-4134, 1997

PubMed 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-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.

PubMed: 9100006
DOI: 10.1021/bi962640d

Experimental method

X-RAY DIFFRACTION (1.8 Å)