View source for 1ay0


==IDENTIFICATION OF CATALYTICALLY IMPORTANT RESIDUES IN YEAST TRANSKETOLASE==
<StructureSection load='1ay0' size='340' side='right'caption='[[1ay0]], [[Resolution|resolution]] 2.60&Aring;' scene=''>
== Structural highlights ==
<table><tr><td colspan='2'>[[1ay0]] is a 2 chain structure with sequence from [https://en.wikipedia.org/wiki/Saccharomyces_cerevisiae Saccharomyces cerevisiae]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=1AY0 OCA]. For a <b>guided tour on the structure components</b> use [https://proteopedia.org/fgij/fg.htm?mol=1AY0 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]] 2.6&#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=TPP:THIAMINE+DIPHOSPHATE'>TPP</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=1ay0 FirstGlance], [http://oca.weizmann.ac.il/oca-bin/ocaids?id=1ay0 OCA], [https://pdbe.org/1ay0 PDBe], [https://www.rcsb.org/pdb/explore.do?structureId=1ay0 RCSB], [https://www.ebi.ac.uk/pdbsum/1ay0 PDBsum], [https://prosat.h-its.org/prosat/prosatexe?pdbcode=1ay0 ProSAT]</span></td></tr>
</table>
== Function ==
[https://www.uniprot.org/uniprot/TKT1_YEAST TKT1_YEAST] Catalyzes the transfer of a two-carbon ketol group from a ketose donor to an aldose acceptor, via a covalent intermediate with the cofactor thiamine pyrophosphate.<ref>PMID:8521838</ref> 
== 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/ay/1ay0_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=1ay0 ConSurf].
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== Publication Abstract from PubMed ==
The possible roles of four histidine residues in the active site of yeast transketolase were examined by site-directed mutagenesis. Replacement of the invariant His69 with alanine yielded a mutant enzyme with 1.5% of the specific activity of the wild-type enzyme and with an increased KM for the donor. This residue is located at the bottom of the substrate cleft close to the C1 hydroxyl group of the donor substrate, and the side chain of His69 might be required for recognition of this hydroxyl group and possibly for maintenance of the proper orientation of the reaction intermediate, (alpha, beta-dihydroxyethyl)thiamin diphosphate. Amino acid replacements of His481 by alanine, serine, and glutamine resulted in mutant enzymes with significantly increased KM values for the donor substrate and specific activities of 4.4%, 1.9%, and 5.5% of the wild-type enzyme. The kinetic data suggest that this residue, although close to the C2 carbonyl oxygen of the substrate, is not absolutely required for stabilization of the negative charge that develops at this oxygen in the transition state. This points toward the 4'-NH2 group of the pyrimidine ring of thiamin diphosphate as the major source of charge stabilization. Mutations at positions His30 and His263 result in mutant enzymes severely impaired in catalytic activity (1.5% and less of the activity of wild-type transketolase). The KM value for the donor substrate was increased for the His30Ala mutant but remained unchanged in the His263Ala enzyme. The side chains of both residues interact with the C3 hydroxyl group of the donor substrate, and the results indicate that the two residues act in concert during proton abstraction of the C3 hydroxyl proton during catalysis.

Identification of catalytically important residues in yeast transketolase.,Wikner C, Nilsson U, Meshalkina L, Udekwu C, Lindqvist Y, Schneider G Biochemistry. 1997 Dec 16;36(50):15643-9. PMID:9398292<ref>PMID:9398292</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 1ay0" style="background-color:#fffaf0;"></div>

==See Also==
*[[Transketolase 3D structures|Transketolase 3D structures]]
== References ==
<references/>
__TOC__
</StructureSection>
[[Category: Large Structures]]
[[Category: Saccharomyces cerevisiae]]
[[Category: Lindqvist Y]]
[[Category: Meshalkina L]]
[[Category: Nilsson U]]
[[Category: Schneider G]]
[[Category: Udekwu C]]
[[Category: Wikner C]]