View source for 1pxg


==Crystal structure of the mutated tRNA-guanine transglycosylase (TGT) D280E complexed with preQ1==
<StructureSection load='1pxg' size='340' side='right'caption='[[1pxg]], [[Resolution|resolution]] 1.70&Aring;' scene=''>
== Structural highlights ==
<table><tr><td colspan='2'>[[1pxg]] is a 1 chain structure with sequence from [https://en.wikipedia.org/wiki/Zymomonas_mobilis Zymomonas mobilis]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=1PXG OCA]. For a <b>guided tour on the structure components</b> use [https://proteopedia.org/fgij/fg.htm?mol=1PXG 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]] 1.7&#8491;</td></tr>
<tr id='ligand'><td class="sblockLbl"><b>[[Ligand|Ligands:]]</b></td><td class="sblockDat" id="ligandDat"><scene name='pdbligand=GOL:GLYCEROL'>GOL</scene>, <scene name='pdbligand=PRF:7-DEAZA-7-AMINOMETHYL-GUANINE'>PRF</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=1pxg FirstGlance], [http://oca.weizmann.ac.il/oca-bin/ocaids?id=1pxg OCA], [https://pdbe.org/1pxg PDBe], [https://www.rcsb.org/pdb/explore.do?structureId=1pxg RCSB], [https://www.ebi.ac.uk/pdbsum/1pxg PDBsum], [https://prosat.h-its.org/prosat/prosatexe?pdbcode=1pxg ProSAT]</span></td></tr>
</table>
== Function ==
[https://www.uniprot.org/uniprot/TGT_ZYMMO TGT_ZYMMO] Exchanges the guanine residue with 7-aminomethyl-7-deazaguanine in tRNAs with GU(N) anticodons (tRNA-Asp, -Asn, -His and -Tyr). After this exchange, a cyclopentendiol moiety is attached to the 7-aminomethyl group of 7-deazaguanine, resulting in the hypermodified nucleoside queuosine (Q) (7-(((4,5-cis-dihydroxy-2-cyclopenten-1-yl)amino)methyl)-7-deazaguanosine).[HAMAP-Rule:MF_00168]
== 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/px/1pxg_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=1pxg ConSurf].
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== Publication Abstract from PubMed ==
tRNA-guanine transglycosylase (TGT) catalyzes a post-transcriptional base-exchange reaction involved in the incorporation of the modified base queuine (Q) into the wobble position of certain tRNAs. Catalysis by TGT occurs through a double-displacement mechanism that involves the formation of a covalent enzyme-RNA intermediate (Kittendorf, J. D., Barcomb, L. M., Nonekowski, S. T., and Garcia, G. A. (2001) Biochemistry 40, 14123-14133). The TGT chemical mechanism requires the protonation of the displaced guanine and the deprotonation of the incoming heterocyclic base. Based on its position in the active site, it is likely that aspartate 264 is involved in these proton transfer events. To investigate this possibility, site-directed mutagenesis was employed to convert aspartate 264 to alanine, asparagine, glutamate, glutamine, lysine, and histidine. Biochemical characterization of these TGT mutants revealed that only the conservative glutamate mutant retained catalytic activity, with Km values for both tRNA and guanine 3-fold greater than those for wild-type, whereas the kcat was depressed by an order of magnitude. Furthermore, of these six TGT mutants, only the TGT(D264E) was capable of forming a TGT.RNA covalent intermediate; however, unlike wild-type TGT, only hydroxylamine is capable of cleaving the TGT(D264E).RNA covalent complex. In an effort to better understand the unique biochemical properties of the D264E TGT mutant, we solved the crystal structure of the Zymomonas mobilis TGT with the analogous mutation (D280E). The results of these studies support two roles for aspartate 264 in catalysis by TGT, protonation of the leaving guanine and deprotonation of the incoming preQ1.

An essential role for aspartate 264 in catalysis by tRNA-guanine transglycosylase from Escherichia coli.,Kittendorf JD, Sgraja T, Reuter K, Klebe G, Garcia GA J Biol Chem. 2003 Oct 24;278(43):42369-76. Epub 2003 Aug 8. PMID:12909636<ref>PMID:12909636</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 1pxg" style="background-color:#fffaf0;"></div>

==See Also==
*[[TRNA-guanine transglycosylase 3D structures|TRNA-guanine transglycosylase 3D structures]]
== References ==
<references/>
__TOC__
</StructureSection>
[[Category: Large Structures]]
[[Category: Zymomonas mobilis]]
[[Category: Garcia GA]]
[[Category: Kittendorf JD]]
[[Category: Klebe G]]
[[Category: Reuter K]]
[[Category: Sgraja T]]