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== Structural highlights ==
== Structural highlights ==
<table><tr><td colspan='2'>[[4ewn]] is a 1 chain structure with sequence from [https://en.wikipedia.org/wiki/Thermotoga_maritima Thermotoga maritima]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=4EWN OCA]. For a <b>guided tour on the structure components</b> use [https://proteopedia.org/fgij/fg.htm?mol=4EWN FirstGlance]. <br>
<table><tr><td colspan='2'>[[4ewn]] is a 1 chain structure with sequence from [https://en.wikipedia.org/wiki/Thermotoga_maritima Thermotoga maritima]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=4EWN OCA]. For a <b>guided tour on the structure components</b> use [https://proteopedia.org/fgij/fg.htm?mol=4EWN FirstGlance]. <br>
</td></tr><tr id='ligand'><td class="sblockLbl"><b>[[Ligand|Ligands:]]</b></td><td class="sblockDat" id="ligandDat"><scene name='pdbligand=0VR:1-(O-CARBOXY-PHENYLAMINO)-1-DEOXY-D-RIBULOSE-5-PHOSPHATE'>0VR</scene></td></tr>
</td></tr><tr id='method'><td class="sblockLbl"><b>[[Empirical_models|Method:]]</b></td><td class="sblockDat" id="methodDat">X-ray diffraction, [[Resolution|Resolution]] 1.903&#8491;</td></tr>
<tr id='ligand'><td class="sblockLbl"><b>[[Ligand|Ligands:]]</b></td><td class="sblockDat" id="ligandDat"><scene name='pdbligand=0VR:1-(O-CARBOXY-PHENYLAMINO)-1-DEOXY-D-RIBULOSE-5-PHOSPHATE'>0VR</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=4ewn FirstGlance], [http://oca.weizmann.ac.il/oca-bin/ocaids?id=4ewn OCA], [https://pdbe.org/4ewn PDBe], [https://www.rcsb.org/pdb/explore.do?structureId=4ewn RCSB], [https://www.ebi.ac.uk/pdbsum/4ewn PDBsum], [https://prosat.h-its.org/prosat/prosatexe?pdbcode=4ewn ProSAT]</span></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=4ewn FirstGlance], [http://oca.weizmann.ac.il/oca-bin/ocaids?id=4ewn OCA], [https://pdbe.org/4ewn PDBe], [https://www.rcsb.org/pdb/explore.do?structureId=4ewn RCSB], [https://www.ebi.ac.uk/pdbsum/4ewn PDBsum], [https://prosat.h-its.org/prosat/prosatexe?pdbcode=4ewn ProSAT]</span></td></tr>
</table>
</table>
== Function ==
== Function ==
[https://www.uniprot.org/uniprot/HIS6_THEMA HIS6_THEMA] IGPS catalyzes the conversion of PRFAR and glutamine to IGP, AICAR and glutamate. The HisF subunit catalyzes the cyclization activity that produces IGP and AICAR from PRFAR using the ammonia provided by the HisH subunit.[HAMAP-Rule:MF_01013]
[https://www.uniprot.org/uniprot/HIS6_THEMA HIS6_THEMA] IGPS catalyzes the conversion of PRFAR and glutamine to IGP, AICAR and glutamate. The HisF subunit catalyzes the cyclization activity that produces IGP and AICAR from PRFAR using the ammonia provided by the HisH subunit.[HAMAP-Rule:MF_01013]
<div style="background-color:#fffaf0;">
== Publication Abstract from PubMed ==
In the course of tryptophan biosynthesis, the isomerization of phosphoribosylanthranilate (PRA) is catalyzed by the (betaalpha)(8)-barrel enzyme TrpF. The reaction occurs via a general acid-base mechanism with an aspartate and a cysteine residue acting as acid and base, respectively. PRA isomerase activity could be established on two (betaalpha)(8)-barrel enzymes involved in histidine biosynthesis, namely HisA and HisF, and on a HisAF chimera, by introducing two aspartate-to-valine substitutions. We have analyzed the reaction mechanism underlying this engineered activity by measuring its pH dependence, solving the crystal structure of a HisF variant with bound product analogue, and applying molecular dynamics simulations and mixed quantum and molecular mechanics calculations. The results suggest that PRA is anchored by the C-terminal phosphate-binding sites of HisA, HisF and HisAF. As a consequence, a conserved aspartate residue, which is equivalent to Cys7 from TrpF, is properly positioned to act as catalytic base. However, no obvious catalytic acid corresponding to Asp126 from TrpF could be identified in the three proteins. Instead, this role appears to be carried out by the carboxylate group of the anthranilate moiety of PRA. Thus, the engineered PRA isomerization activity is based on a reaction mechanism including substrate-assisted catalysis and thus differs substantially from the naturally evolved reaction mechanism used by TrpF.
A sugar isomerization reaction established on various (betaalpha)8-barrel scaffolds is based on substrate-assisted catalysis.,Reisinger B, Bocola M, List F, Claren J, Rajendran C, Sterner R Protein Eng Des Sel. 2012 Nov;25(11):751-60. doi: 10.1093/protein/gzs080. Epub, 2012 Oct 28. PMID:23109729<ref>PMID:23109729</ref>
From MEDLINE&reg;/PubMed&reg;, a database of the U.S. National Library of Medicine.<br>
</div>
<div class="pdbe-citations 4ewn" style="background-color:#fffaf0;"></div>


==See Also==
==See Also==
*[[Indole-3-glycerol phosphate synthase|Indole-3-glycerol phosphate synthase]]
*[[IGPS 3D structures|IGPS 3D structures]]
== References ==
<references/>
__TOC__
__TOC__
</StructureSection>
</StructureSection>

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