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==Crystal Structure of Isoform 2 of Purine Nucleoside Phosphorylase from Schistosoma mansoni in complex with cytosine==
<StructureSection load='5ko5' size='340' side='right'caption='[[5ko5]], [[Resolution|resolution]] 1.36&Aring;' scene=''>
== Structural highlights ==
<table><tr><td colspan='2'>[[5ko5]] is a 1 chain structure with sequence from [https://en.wikipedia.org/wiki/Schistosoma_mansoni Schistosoma mansoni]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=5KO5 OCA]. For a <b>guided tour on the structure components</b> use [https://proteopedia.org/fgij/fg.htm?mol=5KO5 FirstGlance]. <br>
</td></tr><tr id='method'><td class="sblockLbl"><b>[[Empirical_models|Method:]]</b></td><td class="sblockDat" id="methodDat">X-ray diffraction, [[Resolution|Resolution]] 1.36&#8491;</td></tr>
<tr id='ligand'><td class="sblockLbl"><b>[[Ligand|Ligands:]]</b></td><td class="sblockDat" id="ligandDat"><scene name='pdbligand=CYT:6-AMINOPYRIMIDIN-2(1H)-ONE'>CYT</scene>, <scene name='pdbligand=EDO:1,2-ETHANEDIOL'>EDO</scene></td></tr>
<tr id='resources'><td class="sblockLbl"><b>Resources:</b></td><td class="sblockDat"><span class='plainlinks'>[https://proteopedia.org/fgij/fg.htm?mol=5ko5 FirstGlance], [http://oca.weizmann.ac.il/oca-bin/ocaids?id=5ko5 OCA], [https://pdbe.org/5ko5 PDBe], [https://www.rcsb.org/pdb/explore.do?structureId=5ko5 RCSB], [https://www.ebi.ac.uk/pdbsum/5ko5 PDBsum], [https://prosat.h-its.org/prosat/prosatexe?pdbcode=5ko5 ProSAT]</span></td></tr>
</table>
== Function ==
[https://www.uniprot.org/uniprot/A0A0U3AGT1_SCHMA A0A0U3AGT1_SCHMA] The purine nucleoside phosphorylases catalyze the phosphorolytic breakdown of the N-glycosidic bond in the beta-(deoxy)ribonucleoside molecules, with the formation of the corresponding free purine bases and pentose-1-phosphate.[PIRNR:PIRNR000477]
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== Publication Abstract from PubMed ==
Purine nucleoside phosphorylases (PNPs) play an important role in the blood fluke parasite Schistosoma mansoni as a key enzyme of the purine salvage pathway. Here we present the structural and kinetic characterization of a new PNP isoform from S. mansoni, SmPNP2. Thermofluorescence screening of different ligands suggested cytidine and cytosine are potential ligands. The binding of cytosine and cytidine were confirmed by isothermal titration calorimetry, with a KD of 27 muM for cytosine, and a KM of 76.3 muM for cytidine. SmPNP2 also displays catalytic activity against inosine and adenosine, making it the first described PNP with robust catalytic activity towards both pyrimidines and purines. Crystal structures of SmPNP2 with different ligands were obtained and comparison of these structures with the previously described S. mansoni PNP (SmPNP1) provided clues for the unique capacity of SmPNP2 to bind pyrimidines. When compared with the structure of SmPNP1, substitutions in the vicinity of SmPNP2 active site alter the architecture of the nucleoside base binding site thus permitting an alternative binding mode for nucleosides, with a 180 degrees rotation from the canonical binding mode. The remarkable plasticity of this binding site enhances our understanding of the correlation between structure and nucleotide selectivity, thus suggesting new ways to analyse PNP activity.

The molecular structure of Schistosoma mansoni PNP isoform 2 provides insights into the nucleoside selectivity of PNPs.,Torini JR, Romanello L, Batista FAH, Serrao VHB, Faheem M, Zeraik AE, Bird L, Nettleship J, Reddivari Y, Owens R, DeMarco R, Borges JC, Brandao-Neto J, Pereira HD PLoS One. 2018 Sep 7;13(9):e0203532. doi: 10.1371/journal.pone.0203532., eCollection 2018. PMID:30192840<ref>PMID:30192840</ref>

From MEDLINE&reg;/PubMed&reg;, a database of the U.S. National Library of Medicine.<br>
</div>
<div class="pdbe-citations 5ko5" style="background-color:#fffaf0;"></div>

==See Also==
*[[Purine nucleoside phosphorylase 3D structures|Purine nucleoside phosphorylase 3D structures]]
== References ==
<references/>
__TOC__
</StructureSection>
[[Category: Large Structures]]
[[Category: Schistosoma mansoni]]
[[Category: Bird L]]
[[Category: Brandao-Neto J]]
[[Category: Owens R]]
[[Category: Pereira HM]]
[[Category: Romanello L]]
[[Category: Torini JR]]