Open AccessStructure of grouper iridovirus purine nucleoside phosphorylase
Author(s) -
Kang YouNa,
Zhang Yang,
Allan Paula W.,
Parker William B.,
Ting JingWen,
Chang ChiYao,
Ealick Steven E.
Publication year - 2010
Publication title -
acta crystallographica section d
Language(s) - English
Resource type - Journals
ISSN - 1399-0047
DOI - 10.1107/s0907444909048276
Subject(s) - phosphorolysis , purine nucleoside phosphorylase , ribose , stereochemistry , binding site , active site , amino acid , chemistry , nucleoside , biochemistry , purine , enzyme , biology
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 R 3, 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.