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1yqq

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[[Image:1yqq.gif|left|200px]]
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{{STRUCTURE_1yqq| PDB=1yqq | SCENE= }}
{{STRUCTURE_1yqq| PDB=1yqq | SCENE= }}
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'''Escherichia coli purine nucleoside phosphorylase II, the product of the xapA gene'''
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===Escherichia coli purine nucleoside phosphorylase II, the product of the xapA gene===
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==Overview==
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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.
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(as it appears on PubMed at http://www.pubmed.gov), where 15808857 is the PubMed ID number.
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{{ABSTRACT_PUBMED_15808857}}
==About this Structure==
==About this Structure==
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[[Category: Purine nucleoside phosphorylase]]
[[Category: Purine nucleoside phosphorylase]]
[[Category: Xanthine]]
[[Category: Xanthine]]
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''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Sat May 3 16:39:46 2008''
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''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Mon Jul 28 10:23:14 2008''

Revision as of 07:23, 28 July 2008

Image:1yqq.png

Template:STRUCTURE 1yqq

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

Template:ABSTRACT PUBMED 15808857

About this Structure

1YQQ is a Single protein structure of sequence from Escherichia coli. 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

Page seeded by OCA on Mon Jul 28 10:23:14 2008

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