View source for 3etj


==Crystal structure E. coli Purk in complex with Mg, ADP, and Pi==
<StructureSection load='3etj' size='340' side='right'caption='[[3etj]], [[Resolution|resolution]] 1.60&Aring;' scene=''>
== Structural highlights ==
<table><tr><td colspan='2'>[[3etj]] is a 2 chain structure with sequence from [https://en.wikipedia.org/wiki/Escherichia_coli_K-12 Escherichia coli K-12]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=3ETJ OCA]. For a <b>guided tour on the structure components</b> use [https://proteopedia.org/fgij/fg.htm?mol=3ETJ 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]] 1.6&#8491;</td></tr>
<tr id='ligand'><td class="sblockLbl"><b>[[Ligand|Ligands:]]</b></td><td class="sblockDat" id="ligandDat"><scene name='pdbligand=ADP:ADENOSINE-5-DIPHOSPHATE'>ADP</scene>, <scene name='pdbligand=CL:CHLORIDE+ION'>CL</scene>, <scene name='pdbligand=MG:MAGNESIUM+ION'>MG</scene>, <scene name='pdbligand=PI:HYDROGENPHOSPHATE+ION'>PI</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=3etj FirstGlance], [http://oca.weizmann.ac.il/oca-bin/ocaids?id=3etj OCA], [https://pdbe.org/3etj PDBe], [https://www.rcsb.org/pdb/explore.do?structureId=3etj RCSB], [https://www.ebi.ac.uk/pdbsum/3etj PDBsum], [https://prosat.h-its.org/prosat/prosatexe?pdbcode=3etj ProSAT]</span></td></tr>
</table>
== Function ==
[https://www.uniprot.org/uniprot/PURK_ECOLI PURK_ECOLI] Catalyzes the ATP-dependent conversion of 5-aminoimidazole ribonucleotide (AIR) and HCO(3)(-) to N5-carboxyaminoimidazole ribonucleotide (N5-CAIR).
== 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/et/3etj_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=3etj ConSurf].
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== Publication Abstract from PubMed ==
N(5)-Carboxyaminoimidazole ribonucleotide synthetase (N(5)-CAIR synthetase) converts 5-aminoimidazole ribonucleotide (AIR), MgATP, and bicarbonate into N(5)-CAIR, MgADP, and P(i). The enzyme is required for de novo purine biosynthesis in microbes yet is not found in humans suggesting that it represents an ideal and unexplored target for antimicrobial drug design. Here we report the X-ray structures of N(5)-CAIR synthetase from Escherichia coli with either MgATP or MgADP/P(i) bound in the active site cleft. These structures, determined to 1.6-A resolution, provide detailed information regarding the active site geometry before and after ATP hydrolysis. In both structures, two magnesium ions are observed. Each of these is octahedrally coordinated, and the carboxylate side chain of Glu238 bridges them. For the structure of the MgADP/P(i) complex, crystals were grown in the presence of AIR and MgATP. No electron density was observed for AIR, and the electron density corresponding to the nucleotide clearly revealed the presence of ADP and P(i) rather than ATP. The bound P(i) shifts by approximately 3 A relative to the gamma-phosphoryl group of ATP and forms electrostatic interactions with the side chains of Arg242 and His244. Since the reaction mechanism of N(5)-CAIR synthetase is believed to proceed via a carboxyphosphate intermediate, we propose that the location of the inorganic phosphate represents the binding site for stabilization of this reactive species. Using the information derived from the two structures reported here, coupled with molecular modeling, we propose a catalytic mechanism for N(5)-CAIR synthetase.

Structural analysis of the active site geometry of N(5)-Carboxyaminoimidazole ribonucleotide synthetase from Escherichia coli.,Thoden JB, Holden HM, Firestine SM Biochemistry. 2008 Dec 16;47(50):13346-53. PMID:19053251<ref>PMID:19053251</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 3etj" style="background-color:#fffaf0;"></div>

==See Also==
*[[Phosphoribosylaminoimidazole carboxylase 3D structures|Phosphoribosylaminoimidazole carboxylase 3D structures]]
== References ==
<references/>
__TOC__
</StructureSection>
[[Category: Escherichia coli K-12]]
[[Category: Large Structures]]
[[Category: Holden HM]]
[[Category: Thoden JB]]