1yqu
From Proteopedia
(New page: 200px<br /><applet load="1yqu" size="450" color="white" frame="true" align="right" spinBox="true" caption="1yqu, resolution 3.1Å" /> '''Escherichia coli puri...) |
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| - | [[Image:1yqu.gif|left|200px]]<br /><applet load="1yqu" size=" | + | [[Image:1yqu.gif|left|200px]]<br /><applet load="1yqu" size="350" color="white" frame="true" align="right" spinBox="true" |
caption="1yqu, resolution 3.1Å" /> | caption="1yqu, resolution 3.1Å" /> | ||
'''Escherichia coli purine nucleoside phosphorylase II, the product of the xapA gene'''<br /> | '''Escherichia coli purine nucleoside phosphorylase II, the product of the xapA gene'''<br /> | ||
==Overview== | ==Overview== | ||
| - | Purine nucleoside phosphorylases (PNPs, E. C. 2.4.2.1) use orthophosphate | + | 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== | ==About this Structure== | ||
| - | 1YQU is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Escherichia_coli Escherichia coli] with PO4 and GUN as [http://en.wikipedia.org/wiki/ligands ligands]. Full crystallographic information is available from [http:// | + | 1YQU is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Escherichia_coli Escherichia coli] with <scene name='pdbligand=PO4:'>PO4</scene> and <scene name='pdbligand=GUN:'>GUN</scene> as [http://en.wikipedia.org/wiki/ligands ligands]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=1YQU OCA]. |
==Reference== | ==Reference== | ||
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[[Category: Kierdaszuk, B.]] | [[Category: Kierdaszuk, B.]] | ||
[[Category: Shugar, D.]] | [[Category: Shugar, D.]] | ||
| - | [[Category: Szczepanowski, R | + | [[Category: Szczepanowski, R H.]] |
[[Category: GUN]] | [[Category: GUN]] | ||
[[Category: PO4]] | [[Category: PO4]] | ||
[[Category: purine nucleoside phosphorylase guanine xanthine]] | [[Category: purine nucleoside phosphorylase guanine xanthine]] | ||
| - | ''Page seeded by [http:// | + | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Thu Feb 21 16:08:09 2008'' |
Revision as of 14:08, 21 February 2008
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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
1YQU is a Single protein structure of sequence from Escherichia coli with and as ligands. 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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