View source for 1xik

==RIBONUCLEOSIDE-DIPHOSPHATE REDUCTASE 1 BETA CHAIN==
<StructureSection load='1xik' size='340' side='right' caption='[[1xik]], [[Resolution|resolution]] 1.70&Aring;' scene=''>
== Structural highlights ==
<table><tr><td colspan='2'>[[1xik]] is a 2 chain structure with sequence from [http://en.wikipedia.org/wiki/Escherichia_coli Escherichia coli]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=1XIK OCA]. For a <b>guided tour on the structure components</b> use [http://oca.weizmann.ac.il/oca-docs/fgij/fg.htm?mol=1XIK FirstGlance]. <br>
</td></tr><tr><td class="sblockLbl"><b>[[Ligand|Ligands:]]</b></td><td class="sblockDat"><scene name='pdbligand=FE2:FE+(II)+ION'>FE2</scene>, <scene name='pdbligand=HG:MERCURY+(II)+ION'>HG</scene><br>
<tr><td class="sblockLbl"><b>Activity:</b></td><td class="sblockDat"><span class='plainlinks'>[http://en.wikipedia.org/wiki/Ribonucleoside-diphosphate_reductase Ribonucleoside-diphosphate reductase], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=1.17.4.1 1.17.4.1] </span></td></tr>
<tr><td class="sblockLbl"><b>Resources:</b></td><td class="sblockDat"><span class='plainlinks'>[http://oca.weizmann.ac.il/oca-docs/fgij/fg.htm?mol=1xik FirstGlance], [http://oca.weizmann.ac.il/oca-bin/ocaids?id=1xik OCA], [http://www.rcsb.org/pdb/explore.do?structureId=1xik RCSB], [http://www.ebi.ac.uk/pdbsum/1xik PDBsum]</span></td></tr>
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== 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/xi/1xik_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/chain_selection.php?pdb_ID=2ata ConSurf].
<div style="clear:both"></div>
<div style="background-color:#fffaf0;">
== Publication Abstract from PubMed ==
BACKGROUND. Ribonucleotide reductases (RNRs) catalyze the formation of the deoxyribonucleotides that are essential for DNA synthesis. The R2 subunit of Escherichia coli RNR is a homodimer containing one dinuclear iron centre per monomer. A tyrosyl radical is essential for catalysis, and is formed via a reaction in which the reduced, diferrous form of the iron centre activates dioxygen. To help understand the mechanism of oxygen activation, we examined the structure of the diferrous form of R2. RESULTS. The crystal structures of reduced forms of both wild type R2 and a mutant of R2 (Ser211--&gt; Ala) have been determined at 1.7 A and 2.2 A resolution, respectively. The diferrous iron centre was compared to the previously determined structure of the oxidized, diferric form of R2. In both forms of R2 the iron centre is coordinated by the same carboxylate dominated ligand sphere, but in the reduced form there are clear conformational changes in three of the carboxylate ligands and the bridging mu-oxo group and two water molecules are lost. In the reduced form of R2 the coordination number decreases from six to four for both ferrous ions, explaining their high reactivity towards dioxygen. The structure of the mutant Ser211--&gt; Ala, known to have impaired reduction kinetics, shows a large conformational change in one of the neighbouring helices although the iron coordination is very similar to the wild type protein. CONCLUSIONS. Carboxylate shifts are often important for carboxylate coordinated metal clusters; they allow the metals to achieve different coordination modes in redox reactions. In the case of reduced R2 these carboxylate shifts allow the formation of accessible reaction sites for dioxygen. The Ser211--&gt; Ala mutant displays a conformational change in the helix containing the mutation, explaining its altered reduction kinetics.

Crystal structure of reduced protein R2 of ribonucleotide reductase: the structural basis for oxygen activation at a dinuclear iron site.,Logan DT, Su XD, Aberg A, Regnstrom K, Hajdu J, Eklund H, Nordlund P Structure. 1996 Sep 15;4(9):1053-64. PMID:8805591<ref>PMID:8805591</ref>

From MEDLINE&reg;/PubMed&reg;, a database of the U.S. National Library of Medicine.<br>
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==See Also==
*[[Ribonucleotide reductase|Ribonucleotide reductase]]
== References ==
<references/>
__TOC__
</StructureSection>
[[Category: Escherichia coli]]
[[Category: Ribonucleoside-diphosphate reductase]]
[[Category: Aberg, A.]]
[[Category: Eklund, H.]]
[[Category: Hajdu, J.]]
[[Category: Logan, D T.]]
[[Category: Nordlund, P.]]
[[Category: Regnstrom, K.]]
[[Category: Su, X D.]]
[[Category: Dna replication]]
[[Category: Iron]]
[[Category: Oxidoreductase]]