1mas

<StructureSection load='1mas' size='340' side='right' caption='[[1mas]], [[Resolution|resolution]] 2.50&Aring;' scene=''>

<table><tr><td colspan='2'>[[1mas]] is a 2 chain structure with sequence from [http://en.wikipedia.org/wiki/Crithidia_fasciculata Crithidia fasciculata]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=1MAS OCA]. For a <b>guided tour on the structure components</b> use [http://oca.weizmann.ac.il/oca-docs/fgij/fg.htm?mol=1MAS FirstGlance]. <br>

</td></tr><tr><td class="sblockLbl"><b>[[Ligand|Ligands:]]</b></td><td class="sblockDat"><scene name='pdbligand=K:POTASSIUM+ION'>K</scene><br>

<tr><td class="sblockLbl"><b>[[Gene|Gene:]]</b></td><td class="sblockDat">IU-NH FROM C.FASCICULATA ([http://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?mode=Info&srchmode=5&id=5656 Crithidia fasciculata])</td></tr>

<tr><td class="sblockLbl"><b>Activity:</b></td><td class="sblockDat"><span class='plainlinks'>[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] </span></td></tr>

<tr><td class="sblockLbl"><b>Resources:</b></td><td class="sblockDat"><span class='plainlinks'>[http://oca.weizmann.ac.il/oca-docs/fgij/fg.htm?mol=1mas FirstGlance], [http://oca.weizmann.ac.il/oca-bin/ocaids?id=1mas OCA], [http://www.rcsb.org/pdb/explore.do?structureId=1mas RCSB], [http://www.ebi.ac.uk/pdbsum/1mas PDBsum]</span></td></tr>

<table>

<scriptWhenChecked>select protein; define ~consurf_to_do selected; consurf_initial_scene = true; script "/wiki/ConSurf/ma/1mas_consurf.spt"</scriptWhenChecked>

</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/chain_selection.php?pdb_ID=2ata ConSurf].

<div style="background-color:#fffaf0;">

== Publication Abstract from PubMed ==

Protozoan parasites rely on the host for purines since they lack a de novo synthetic pathway. Crithidia fasciculata salvages exogenous inosine primarily through hydrolysis of the N-ribosidic bond using several nucleoside hydrolases. The most abundant nucleoside hydrolase is relatively nonspecific but prefers inosine and uridine as substrates. Here we report the three-dimensional structure of the inosine-uridine nucleoside hydrolase (IU-NH) from C. fasciculata determined by X-ray crystallography at a nominal resolution of 2.5 A. The enzyme has an open (alpha, beta) structure which differs from the classical dinucleotide binding fold. IU-nucleoside hydrolase is composed of a mixed eight-stranded beta sheet surrounded by six alpha helices and a small C-terminal lobe composed of four alpha helices. Two short antiparallel beta strands are involved in intermolecular contacts. The catalytic pocket is located at the C-terminal end of beta strands beta 1 and beta 4. Four aspartate residues are located at the bottom of the cavity in a geometry which suggests interaction with the ribose moiety of the nucleoside. These groups could provide the catalytically important interactions to the ribosyl hydroxyls and the stabilizing anion for the oxycarbonium-like transition state. Histidine 241, located on the side of the active site cavity, is the proposed proton donor which facilitates purine base departure [Gopaul, D. N., Meyer, S. L., Degano, M., Sacchettini, J. C., &amp; Schramm, V. L. (1996) Biochemistry 35, 5963-5970]. The substrate binding site is unlike that from purine nucleoside phosphorylase, phosphoribosyltransferases, or uracil DNA glycosylase and thus represents a novel architecture for general acid-base catalysis. This detailed knowledge of the architecture of the active site, together with the previous transition state analysis [Horenstein, B. A., Parkin, D. W., Estupinan, B., &amp; Schramm, V. L. (1991) Biochemistry 30, 10788-10795], allows analysis of the interactions leading to catalysis and an explanation for the tight-binding inhibitors of the enzyme [Schramm, V. L., Horenstein, B. A., &amp; Kline, P. C. (1994) J. Biol. Chem. 269, 18259-18262].

Three-dimensional structure of the inosine-uridine nucleoside N-ribohydrolase from Crithidia fasciculata.,Degano M, Gopaul DN, Scapin G, Schramm VL, Sacchettini JC Biochemistry. 1996 May 14;35(19):5971-81. PMID:8634238<ref>PMID:8634238</ref>

From MEDLINE&reg;/PubMed&reg;, a database of the U.S. National Library of Medicine.<br>

</div>

== References ==

<references/>

[[Category: Purine nucleosidase]]

[[Category: Degano, M.]]

[[Category: Gopaul, D N.]]

[[Category: Sacchettini, J C.]]

[[Category: Scapin, G.]]

[[Category: Schramm, V L.]]

[[Category: Purine nucleoside hydrolase]]