1YQQ

Escherichia coli purine nucleoside phosphorylase II, the product of the xapA gene

Summary for 1YQQ

• Entry DOI: 10.2210/pdb1yqq/pdb
• Descriptor: Xanthosine phosphorylase, PHOSPHATE ION, GUANINE, ... (4 entities in total)
• Functional Keywords: purine nucleoside phosphorylase, guanine, xanthine, transferase
• Biological source: Escherichia coli
• Total number of polymer chains: 3
• Total formula weight: 90335.06

Authors

Dandanell, G.,Szczepanowski, R.H.,Kierdaszuk, B.,Shugar, D.,Bochtler, M. (deposition date: 2005-02-02, release date: 2005-04-19, Last modification date: 2024-04-03)

Primary citation

Dandanell, G.,Szczepanowski, R.H.,Kierdaszuk, B.,Shugar, D.,Bochtler, M.
Escherichia coli Purine Nucleoside Phosphorylase II, the Product of the xapA Gene
J.Mol.Biol., 348:113-125, 2005

PubMed Abstract: Purine nucleoside phosphorylases (PNPs, E. C. 2.4.2.1) use orthophosphate to cleave the N-glycosidic bond of beta-(deoxy)ribonucleosides to yield alpha-(deoxy)ribose 1-phosphate and the free purine base. Escherichia coli PNP-II, the product of the xapA gene, is similar to trimeric PNPs in sequence, but has been reported to migrate as a hexamer and to accept xanthosine with comparable efficiency to guanosine and inosine, the usual physiological substrates for trimeric PNPs. Here, we present a detailed biochemical characterization and the crystal structure of E.coli PNP-II. In three different crystal forms, PNP-II trimers dimerize, leading to a subunit arrangement that is qualitatively different from the "trimer of dimers" arrangement of conventional high molecular mass PNPs. Crystal structures are compatible with similar binding modes for guanine and xanthine, with a preference for the neutral over the monoanionic form of xanthine. A single amino acid exchange, tyrosine 191 to leucine, is sufficient to convert E.coli PNP-II into an enzyme with the specificity of conventional trimeric PNPs, but the reciprocal mutation in human PNP, valine 195 to tyrosine, does not elicit xanthosine phosphorylase activity in the human enzyme.

PubMed: 15808857
DOI: 10.1016/j.jmb.2005.02.019

Experimental method

X-RAY DIFFRACTION (2.6 Å)