Steve Ealick's Research Group
Grouper Iridovirus Purine Nucleoside Phosphorylase
Purine nucleoside phosphorylase (PNP) catalyzes the reversible phosphorolysis of purine ribonucleosides to the corresponding free bases and ribose 1-phosphate. The iridovirus that infects grouper fish represents the first instance in which the PNP gene has been found in a virus.
The core of the givPNP protomer has an α/β structure with a nine-stranded mixed β-barrel surrounded by four α-helices on one side and five on the other side.
|The overall structure of givPNP is a homotrimer that is similar to the structures of human PNP and bovine PNP. In givPNP, there is a disulfide bond between Cys203 and Cys246 in a flexible loop region. The rigid disulfide bond alters the first part of this loop resulting in a conformation different from the mammalian PNPs.|
The active sites, which are located at the trimer interface and formed by residues from two adjacent protomers, are occupied by a phosphate ion and a Tris molecule.
Kang YN, Zhang Y, Allan PW, Parker WB, Ting JW, Chang CY and Ealick SE. Crystal Structure of Grouper Iridovirus Purine Nucleoside Phosphorylase.Acta Crystallogr. D 66:155-162 (2010).