View source for 3sce

==Structure of the Thioalkalivibrio nitratireducens cytochrome c nitrite reductase with a covalent bond between the CE1 atom of Tyr303 and the CG atom of Gln360 (TvNiRb)==
<StructureSection load='3sce' size='340' side='right' caption='[[3sce]], [[Resolution|resolution]] 1.45&Aring;' scene=''>
== Structural highlights ==
<table><tr><td colspan='2'>[[3sce]] is a 2 chain structure with sequence from [http://en.wikipedia.org/wiki/Thioalkalivibrio_nitratireducens Thioalkalivibrio nitratireducens]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=3SCE OCA]. For a <b>guided tour on the structure components</b> use [http://oca.weizmann.ac.il/oca-docs/fgij/fg.htm?mol=3SCE FirstGlance]. <br>
</td></tr><tr id='ligand'><td class="sblockLbl"><b>[[Ligand|Ligands:]]</b></td><td class="sblockDat"><scene name='pdbligand=CA:CALCIUM+ION'>CA</scene>, <scene name='pdbligand=HEC:HEME+C'>HEC</scene>, <scene name='pdbligand=NA:SODIUM+ION'>NA</scene>, <scene name='pdbligand=PG4:TETRAETHYLENE+GLYCOL'>PG4</scene>, <scene name='pdbligand=PG6:1-(2-METHOXY-ETHOXY)-2-{2-[2-(2-METHOXY-ETHOXY]-ETHOXY}-ETHANE'>PG6</scene>, <scene name='pdbligand=PO4:PHOSPHATE+ION'>PO4</scene></td></tr>
<tr id='related'><td class="sblockLbl"><b>[[Related_structure|Related:]]</b></td><td class="sblockDat">[[2ot4|2ot4]]</td></tr>
<tr id='resources'><td class="sblockLbl"><b>Resources:</b></td><td class="sblockDat"><span class='plainlinks'>[http://oca.weizmann.ac.il/oca-docs/fgij/fg.htm?mol=3sce FirstGlance], [http://oca.weizmann.ac.il/oca-bin/ocaids?id=3sce OCA], [http://www.rcsb.org/pdb/explore.do?structureId=3sce RCSB], [http://www.ebi.ac.uk/pdbsum/3sce PDBsum]</span></td></tr>
</table>
<div style="background-color:#fffaf0;">
== Publication Abstract from PubMed ==
Octahaem cytochrome c nitrite reductase from Thioalkalivibrio nitratireducens (TvNiR), like the previously characterized pentahaem nitrite reductases (NrfAs), catalyzes the six-electron reductions of nitrite to ammonia and of sulfite to sulfide. The active site of both TvNiR and NrfAs is formed by the lysine-coordinated haem and His, Tyr and Arg residues. The distinguishing structural feature of TvNiR is the presence of a covalent bond between the CE2 atom of the catalytic Tyr303 and the S atom of Cys305, which might be responsible for the higher nitrite reductase activity of TvNiR compared with NrfAs. In the present study, a new modified form of the enzyme (TvNiRb) that contains an additional covalent bond between Tyr303 CE1 and Gln360 CG is reported. Structures of TvNiRb in complexes with phosphate (1.45 A resolution) and sulfite (1.8 A resolution), the structure of TvNiR in a complex with nitrite (1.83 A resolution) and several additional structures were determined. The formation of the second covalent bond by Tyr303 leads to a decrease in both the nitrite and sulfite reductase activities of the enzyme. Tyr303 is located at the exit from the putative proton-transport channel to the active site, which is absent in NrfAs. This is an additional argument in favour of the involvement of Tyr303 as a proton donor in catalysis. The changes in the activity of cytochrome c nitrite reductases owing to the formation of Tyr-Cys and Tyr-Gln bonds may be associated with changes in the pK(a) value of the catalytic tyrosine.

Covalent modifications of the catalytic tyrosine in octahaem cytochrome c nitrite reductase and their effect on the enzyme activity.,Trofimov AA, Polyakov KM, Tikhonova TV, Tikhonov AV, Safonova TN, Boyko KM, Dorovatovskii PV, Popov VO Acta Crystallogr D Biol Crystallogr. 2012 Feb;68(Pt 2):144-53. Epub 2012, Jan 13. PMID:22281743<ref>PMID:22281743</ref>

From MEDLINE&reg;/PubMed&reg;, a database of the U.S. National Library of Medicine.<br>
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==See Also==
*[[Nitric reductase|Nitric reductase]]
== References ==
<references/>
__TOC__
</StructureSection>
[[Category: Thioalkalivibrio nitratireducens]]
[[Category: Boyko, K M]]
[[Category: Polyakov, K M]]
[[Category: Popov, V O]]
[[Category: Tikhonova, T V]]
[[Category: Trofimov, A A]]
[[Category: Eight hemes c]]
[[Category: Nitrite reductase]]
[[Category: Oxidoreductase]]
[[Category: Tyr-gln and tyr-cys bond]]