View source for 3hka


==Crystal structure of uronate isomerase from Bacillus halodurans complexed with zinc and D-Fructuronate==
<StructureSection load='3hka' size='340' side='right'caption='[[3hka]], [[Resolution|resolution]] 1.90&Aring;' scene=''>
== Structural highlights ==
<table><tr><td colspan='2'>[[3hka]] is a 3 chain structure with sequence from [https://en.wikipedia.org/wiki/Alkalihalobacillus_halodurans_C-125 Alkalihalobacillus halodurans C-125]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=3HKA OCA]. For a <b>guided tour on the structure components</b> use [https://proteopedia.org/fgij/fg.htm?mol=3HKA 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]] 1.9&#8491;</td></tr>
<tr id='ligand'><td class="sblockLbl"><b>[[Ligand|Ligands:]]</b></td><td class="sblockDat" id="ligandDat"><scene name='pdbligand=CL:CHLORIDE+ION'>CL</scene>, <scene name='pdbligand=CO3:CARBONATE+ION'>CO3</scene>, <scene name='pdbligand=FIX:D-FRUCTURONIC+ACID'>FIX</scene>, <scene name='pdbligand=ZN:ZINC+ION'>ZN</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=3hka FirstGlance], [http://oca.weizmann.ac.il/oca-bin/ocaids?id=3hka OCA], [https://pdbe.org/3hka PDBe], [https://www.rcsb.org/pdb/explore.do?structureId=3hka RCSB], [https://www.ebi.ac.uk/pdbsum/3hka PDBsum], [https://prosat.h-its.org/prosat/prosatexe?pdbcode=3hka ProSAT]</span></td></tr>
</table>
== Function ==
[https://www.uniprot.org/uniprot/Q9KFI6_HALH5 Q9KFI6_HALH5] 
== 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/hk/3hka_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=3hka ConSurf].
<div style="clear:both"></div>
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== Publication Abstract from PubMed ==
Uronate isomerase (URI) catalyzes the reversible isomerization of D-glucuronate to D-fructuronate and of D-galacturonate to D-tagaturonate. URI is a member of the amidohydrolase superfamily (AHS), a highly divergent group of enzymes that catalyzes primarily hydrolytic reactions. The chemical mechanism and active site structure of URI was investigated in an attempt to obtain a greater understanding of how an active site template that apparently evolved to catalyze hydrolytic reactions has been re-forged to catalyze an isomerization reaction. The pH-rate profiles for kcat and kcat/Km for URI from Escherichia coli are bell-shaped and indicate that one group must be unprotonated and another residue must be protonated for catalytic activity. Primary isotope effects on the kinetic constants with [2-2H]-D-glucuronate and the effects of changes in solvent viscosity are consistent with product release as the rate limiting step. The X-ray structure of Bh0493, a URI from Bacillus halodurans, was determined in the presence of the substrate D-glucuronate. The bound complex showed that the mononuclear metal center in the active site is ligated to the C-6 carboxylate and the C-5 hydroxyl group of the substrate. This hydroxyl group is also hydrogen bonded to Asp-355 in the same orientation as the hydroxide/water is bound in those members of the AHS that catalyze hydrolytic reactions. In addition, the C-2 and C-3 hydroxyl groups of the substrate are hydrogen bonded to Arg-357 and the carbonyl group at C-1 is hydrogen bonded to Tyr-50. A chemical mechanism is proposed that utilizes a proton transfer from C-2 of D-glucuronate to C-1 that is initiated by the combined actions of Asp-355 from the end of beta-strand 8 and the C-5 hydroxyl of the substrate that is bound to the metal ion. The formation of the cis-enediol intermediate is further facilitated by the shuttling of the proton between the C-2 and C-1 oxygens by the conserved Tyr-50 and/or Arg-355.

The Mechanism of the Reaction Catalyzed by Uronate Isomerase Illustrates How an Isomerase May Have Evolved from a Hydrolase within the Amidohydrolase Superfamily.,Nguyen TT, Fedorov AA, Williams L, Fedorov EV, Li Y, Xu C, Almo SC, Raushel FM Biochemistry. 2009 Aug 14. PMID:19678710<ref>PMID:19678710</ref>

From MEDLINE&reg;/PubMed&reg;, a database of the U.S. National Library of Medicine.<br>
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<div class="pdbe-citations 3hka" style="background-color:#fffaf0;"></div>
== References ==
<references/>
__TOC__
</StructureSection>
[[Category: Alkalihalobacillus halodurans C-125]]
[[Category: Large Structures]]
[[Category: Almo SC]]
[[Category: Fedorov AA]]
[[Category: Fedorov EV]]
[[Category: Nguyen TT]]
[[Category: Raushel FM]]