View source for 2jio


==A New Catalytic Mechanism of Periplasmic Nitrate Reductase from Desulfovibrio desulfuricans ATCC 27774 from Crystallographic and EPR Data and based on detailed analysis of the sixth ligand==
<StructureSection load='2jio' size='340' side='right'caption='[[2jio]], [[Resolution|resolution]] 2.20&Aring;' scene=''>
== Structural highlights ==
<table><tr><td colspan='2'>[[2jio]] is a 1 chain structure with sequence from [https://en.wikipedia.org/wiki/Desulfovibrio_desulfuricans Desulfovibrio desulfuricans]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=2JIO OCA]. For a <b>guided tour on the structure components</b> use [https://proteopedia.org/fgij/fg.htm?mol=2JIO 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]] 2.2&#8491;</td></tr>
<tr id='ligand'><td class="sblockLbl"><b>[[Ligand|Ligands:]]</b></td><td class="sblockDat" id="ligandDat"><scene name='pdbligand=MGD:2-AMINO-5,6-DIMERCAPTO-7-METHYL-3,7,8A,9-TETRAHYDRO-8-OXA-1,3,9,10-TETRAAZA-ANTHRACEN-4-ONE+GUANOSINE+DINUCLEOTIDE'>MGD</scene>, <scene name='pdbligand=MO:MOLYBDENUM+ATOM'>MO</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=2jio FirstGlance], [http://oca.weizmann.ac.il/oca-bin/ocaids?id=2jio OCA], [https://pdbe.org/2jio PDBe], [https://www.rcsb.org/pdb/explore.do?structureId=2jio RCSB], [https://www.ebi.ac.uk/pdbsum/2jio PDBsum], [https://prosat.h-its.org/prosat/prosatexe?pdbcode=2jio ProSAT]</span></td></tr>
</table>
== Function ==
[https://www.uniprot.org/uniprot/NAPA_DESDA NAPA_DESDA] Catalytic subunit of the periplasmic nitrate reductase (NAP). Only expressed at high levels during aerobic growth. NapAB complex receives electrons from the membrane-anchored tetraheme protein NapC, thus allowing electron flow between membrane and periplasm. Essential function for nitrate assimilation and may have a role in anaerobic metabolism.
== 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/ji/2jio_consurf.spt"</scriptWhenChecked>
    <scriptWhenUnchecked>script /wiki/extensions/Proteopedia/spt/initialview03.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=2jio ConSurf].
<div style="clear:both"></div>
<div style="background-color:#fffaf0;">
== Publication Abstract from PubMed ==
Nitrate reductase from Desulfovibrio desulfuricans ATCC 27774 (DdNapA) is a monomeric protein of 80 kDa harboring a bis(molybdopterin guanine dinucleotide) active site and a [4Fe-4S] cluster. Previous electron paramagnetic resonance (EPR) studies in both catalytic and inhibiting conditions showed that the molybdenum center has high coordination flexibility when reacted with reducing agents, substrates or inhibitors. As-prepared DdNapA samples, as well as those reacted with substrates and inhibitors, were crystallized and the corresponding structures were solved at resolutions ranging from 1.99 to 2.45 A. The good quality of the diffraction data allowed us to perform a detailed structural study of the active site and, on that basis, the sixth molybdenum ligand, originally proposed to be an OH/OH(2) ligand, was assigned as a sulfur atom after refinement and analysis of the B factors of all the structures. This unexpected result was confirmed by a single-wavelength anomalous diffraction experiment below the iron edge (lambda = 1.77 A) of the as-purified enzyme. Furthermore, for six of the seven datasets, the S-S distance between the sulfur ligand and the Sgamma atom of the molybdenum ligand Cys(A140) was substantially shorter than the van der Waals contact distance and varies between 2.2 and 2.85 A, indicating a partial disulfide bond. Preliminary EPR studies under catalytic conditions showed an EPR signal designated as a turnover signal (g values 1.999, 1.990, 1.982) showing hyperfine structure originating from a nucleus of unknown nature. Spectropotentiometric studies show that reduced methyl viologen, the electron donor used in the catalytic reaction, does not interact directly with the redox cofactors. The turnover signal can be obtained only in the presence of the reaction substrates. With use of the optimized conditions determined by spectropotentiometric titration, the turnover signal was developed with (15)N-labeled nitrate and in D(2)O-exchanged DdNapA samples. These studies indicate that this signal is not associated with a Mo(V)-nitrate adduct and that the hyperfine structure originates from two equivalent solvent-exchangeable protons. The new coordination sphere of molybdenum proposed on the basis of our studies led us to revise the currently accepted reaction mechanism for periplasmic nitrate reductases. Proposals for a new mechanism are discussed taking into account a molybdenum and ligand-based redox chemistry, rather than the currently accepted redox chemistry based solely on the molybdenum atom.

Periplasmic nitrate reductase revisited: a sulfur atom completes the sixth coordination of the catalytic molybdenum.,Najmudin S, Gonzalez PJ, Trincao J, Coelho C, Mukhopadhyay A, Cerqueira NM, Romao CC, Moura I, Moura JJ, Brondino CD, Romao MJ J Biol Inorg Chem. 2008 Mar 8;. PMID:18327621<ref>PMID:18327621</ref>

From MEDLINE&reg;/PubMed&reg;, a database of the U.S. National Library of Medicine.<br>
</div>
<div class="pdbe-citations 2jio" style="background-color:#fffaf0;"></div>

==See Also==
*[[Nitrate reductase|Nitrate reductase]]
== References ==
<references/>
__TOC__
</StructureSection>
[[Category: Desulfovibrio desulfuricans]]
[[Category: Large Structures]]
[[Category: Brondino CD]]
[[Category: Coelho C]]
[[Category: Gonzalez PJ]]
[[Category: Moura I]]
[[Category: Moura JJG]]
[[Category: Mukhopadhyay A]]
[[Category: Najmudin S]]
[[Category: Romao CC]]
[[Category: Romao MJ]]
[[Category: Trincao J]]