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[[Image:2mas.gif|left|200px]]<br />
<applet load="2mas" size="450" color="white" frame="true" align="right" spinBox="true"
caption="2mas, resolution 2.3&Aring;" />
'''PURINE NUCLEOSIDE HYDROLASE WITH A TRANSITION STATE INHIBITOR'''<br />


==Overview==
==PURINE NUCLEOSIDE HYDROLASE WITH A TRANSITION STATE INHIBITOR==
Nucleoside N-ribohydrolases are targets for disruption of purine salvage, in the protozoan parasites. The structure of a trypanosomal, N-ribohydrolase in complex with a transition-state inhibitor is reported, at 2.3 A resolution. The nonspecific nucleoside hydrolase from Crithidia, fasciculata cocrystallized with p-aminophenyliminoribitol reveals tightly, bound Ca2+ as a catalytic site ligand. The complex with the, transition-state inhibitor is characterized by (1) large protein, conformational changes to create a hydrophobic leaving group site (2), C3'-exo geometry for the inhibitor, typical of a ribooxocarbenium ion (3), stabilization of the ribooxocarbenium analogue between the neighboring, group 5'-hydroxyl and bidentate hydrogen bonds to Asn168; and (4), octacoordinate Ca2+ orients a ... [[http://ispc.weizmann.ac.il/pmbin/getpm?9572842 (full description)]]
<StructureSection load='2mas' size='340' side='right'caption='[[2mas]], [[Resolution|resolution]] 2.30&Aring;' scene=''>
== Structural highlights ==
<table><tr><td colspan='2'>[[2mas]] is a 4 chain structure with sequence from [https://en.wikipedia.org/wiki/Crithidia_fasciculata Crithidia fasciculata]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=2MAS OCA]. For a <b>guided tour on the structure components</b> use [https://proteopedia.org/fgij/fg.htm?mol=2MAS 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]] 2.3&#8491;</td></tr>
<tr id='ligand'><td class="sblockLbl"><b>[[Ligand|Ligands:]]</b></td><td class="sblockDat" id="ligandDat"><scene name='pdbligand=CA:CALCIUM+ION'>CA</scene>, <scene name='pdbligand=PIR:2-(4-AMINO-PHENYL)-5-HYDROXYMETHYL-PYRROLIDINE-3,4-DIOL'>PIR</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=2mas FirstGlance], [http://oca.weizmann.ac.il/oca-bin/ocaids?id=2mas OCA], [https://pdbe.org/2mas PDBe], [https://www.rcsb.org/pdb/explore.do?structureId=2mas RCSB], [https://www.ebi.ac.uk/pdbsum/2mas PDBsum], [https://prosat.h-its.org/prosat/prosatexe?pdbcode=2mas ProSAT]</span></td></tr>
</table>
== Function ==
[https://www.uniprot.org/uniprot/IUNH_CRIFA IUNH_CRIFA] Catalyzes the hydrolysis of all of the commonly occurring purine and pyrimidine nucleosides into ribose and the associated base, but has a preference for inosine and uridine as substrates.
== Evolutionary Conservation ==
[[Image:Consurf_key_small.gif|200px|right]]
Check<jmol>
  <jmolCheckbox>
    <scriptWhenChecked>; select protein; define ~consurf_to_do selected; consurf_initial_scene = true; script "/wiki/ConSurf/ma/2mas_consurf.spt"</scriptWhenChecked>
    <scriptWhenUnchecked>script /wiki/extensions/Proteopedia/spt/initialview01.spt</scriptWhenUnchecked>
    <text>to colour the structure by Evolutionary Conservation</text>
  </jmolCheckbox>
</jmol>, as determined by [http://consurfdb.tau.ac.il/ ConSurfDB]. You may read the [[Conservation%2C_Evolutionary|explanation]] of the method and the full data available from [http://bental.tau.ac.il/new_ConSurfDB/main_output.php?pdb_ID=2mas ConSurf].
<div style="clear:both"></div>
<div style="background-color:#fffaf0;">
== Publication Abstract from PubMed ==
Nucleoside N-ribohydrolases are targets for disruption of purine salvage in the protozoan parasites. The structure of a trypanosomal N-ribohydrolase in complex with a transition-state inhibitor is reported at 2.3 A resolution. The nonspecific nucleoside hydrolase from Crithidia fasciculata cocrystallized with p-aminophenyliminoribitol reveals tightly bound Ca2+ as a catalytic site ligand. The complex with the transition-state inhibitor is characterized by (1) large protein conformational changes to create a hydrophobic leaving group site (2) C3'-exo geometry for the inhibitor, typical of a ribooxocarbenium ion (3) stabilization of the ribooxocarbenium analogue between the neighboring group 5'-hydroxyl and bidentate hydrogen bonds to Asn168; and (4) octacoordinate Ca2+ orients a catalytic site water and is liganded to two hydroxyls of the inhibitor. The mechanism is ribooxocarbenium stabilization with weak leaving group activation and is a departure from glucohydrolases which use paired carboxylates to achieve the transition state.


==About this Structure==
Trypanosomal nucleoside hydrolase. A novel mechanism from the structure with a transition-state inhibitor.,Degano M, Almo SC, Sacchettini JC, Schramm VL Biochemistry. 1998 May 5;37(18):6277-85. PMID:9572842<ref>PMID:9572842</ref>
2MAS is a [[http://en.wikipedia.org/wiki/Single_protein Single protein]] structure of sequence from [[http://en.wikipedia.org/wiki/Crithidia_fasciculata Crithidia fasciculata]] with CA and PIR as [[http://en.wikipedia.org/wiki/ligands ligands]]. Active as [[http://en.wikipedia.org/wiki/Purine_nucleosidase Purine nucleosidase]], with EC number [[http://www.brenda-enzymes.info/php/result_flat.php4?ecno=3.2.2.1 3.2.2.1]]. Structure known Active Sites: S1, S2, S3 and S4. Full crystallographic information is available from [[http://ispc.weizmann.ac.il/oca-bin/ocashort?id=2MAS OCA]].


==Reference==
From MEDLINE&reg;/PubMed&reg;, a database of the U.S. National Library of Medicine.<br>
Trypanosomal nucleoside hydrolase. A novel mechanism from the structure with a transition-state inhibitor., Degano M, Almo SC, Sacchettini JC, Schramm VL, Biochemistry. 1998 May 5;37(18):6277-85. PMID:[http://ispc.weizmann.ac.il//pmbin/getpm?pmid=9572842 9572842]
</div>
<div class="pdbe-citations 2mas" style="background-color:#fffaf0;"></div>
== References ==
<references/>
__TOC__
</StructureSection>
[[Category: Crithidia fasciculata]]
[[Category: Crithidia fasciculata]]
[[Category: Purine nucleosidase]]
[[Category: Large Structures]]
[[Category: Single protein]]
[[Category: Degano M]]
[[Category: Degano, M.]]
[[Category: Sacchettini JC]]
[[Category: Sacchettini, J.C.]]
[[Category: Schramm VL]]
[[Category: Schramm, V.L.]]
[[Category: CA]]
[[Category: PIR]]
[[Category: hydrolase]]
[[Category: inosine]]
[[Category: iu-nh]]
[[Category: purine nucleosidase]]
[[Category: purine nucleoside hydrolase]]
[[Category: uridine]]
 
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