Structure of grouper iridovirus purine nucleoside phosphorylase
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, NY 14853-1301 (United States)
- Southern Research Institute, Birmingham, AL 35205 (United States)
- The Institute of Cellular and Organismic Biology, Academia Sinica, Taipei 115,Taiwan (China)
The crystal structure of purine nucleoside phosphorylase from grouper iridovirus was solved at 2.38 Å resolution. Purine nucleoside phosphorylase (PNP) catalyzes the reversible phosphorolysis of purine ribonucleosides to the corresponding free bases and ribose 1-phosphate. The crystal structure of grouper iridovirus PNP (givPNP), corresponding to the first PNP gene to be found in a virus, was determined at 2.4 Å resolution. The crystals belonged to space group R3, with unit-cell parameters a = 193.0, c = 105.6 Å, and contained four protomers per asymmetric unit. The overall structure of givPNP shows high similarity to mammalian PNPs, having an α/β structure with a nine-stranded mixed β-barrel flanked by a total of nine α-helices. The predicted phosphate-binding and ribose-binding sites are occupied by a phosphate ion and a Tris molecule, respectively. The geometrical arrangement and hydrogen-bonding patterns of the phosphate-binding site are similar to those found in the human and bovine PNP structures. The enzymatic activity assay of givPNP on various substrates revealed that givPNP can only accept 6-oxopurine nucleosides as substrates, which is also suggested by its amino-acid composition and active-site architecture. All these results suggest that givPNP is a homologue of mammalian PNPs in terms of amino-acid sequence, molecular mass, substrate specificity and overall structure, as well as in the composition of the active site.
- OSTI ID:
- 22351201
- Journal Information:
- Acta Crystallographica. Section D: Biological Crystallography, Journal Name: Acta Crystallographica. Section D: Biological Crystallography Journal Issue: Pt 2 Vol. 66; ISSN 0907-4449; ISSN ABCRE6
- Country of Publication:
- Denmark
- Language:
- English
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