1yqq
From Proteopedia
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Escherichia coli purine nucleoside phosphorylase II, the product of the xapA gene
Overview
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.
About this Structure
1YQQ is a Single protein structure of sequence from Escherichia coli with PO4 and GUN as ligands. Active as Purine-nucleoside phosphorylase, with EC number 2.4.2.1 Full crystallographic information is available from OCA.
Reference
Escherichia coli purine nucleoside phosphorylase II, the product of the xapA gene., Dandanell G, Szczepanowski RH, Kierdaszuk B, Shugar D, Bochtler M, J Mol Biol. 2005 Apr 22;348(1):113-25. PMID:15808857
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