View source for 8gep


==SULFITE REDUCTASE HEMOPROTEIN NITRATE COMPLEX==
<StructureSection load='8gep' size='340' side='right'caption='[[8gep]], [[Resolution|resolution]] 2.20&Aring;' scene=''>
== Structural highlights ==
<table><tr><td colspan='2'>[[8gep]] is a 1 chain structure with sequence from [https://en.wikipedia.org/wiki/Escherichia_coli_B Escherichia coli B]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=8GEP OCA]. For a <b>guided tour on the structure components</b> use [https://proteopedia.org/fgij/fg.htm?mol=8GEP 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=K:POTASSIUM+ION'>K</scene>, <scene name='pdbligand=NO3:NITRATE+ION'>NO3</scene>, <scene name='pdbligand=SRM:SIROHEME'>SRM</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=8gep FirstGlance], [http://oca.weizmann.ac.il/oca-bin/ocaids?id=8gep OCA], [https://pdbe.org/8gep PDBe], [https://www.rcsb.org/pdb/explore.do?structureId=8gep RCSB], [https://www.ebi.ac.uk/pdbsum/8gep PDBsum], [https://prosat.h-its.org/prosat/prosatexe?pdbcode=8gep ProSAT]</span></td></tr>
</table>
== Function ==
[https://www.uniprot.org/uniprot/CYSI_ECOLI CYSI_ECOLI] Component of the sulfite reductase complex that catalyzes the 6-electron reduction of sulfite to sulfide. This is one of several activities required for the biosynthesis of L-cysteine from sulfate.[HAMAP-Rule:MF_01540]
== 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/ge/8gep_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=8gep ConSurf].
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== Publication Abstract from PubMed ==
To further understand the six-electron reductions of sulfite and nitrite catalyzed by the Escherichia coli sulfite reductase hemoprotein (SiRHP), we have determined crystallographic structures of the enzyme in complex with the inhibitors phosphate, carbon monoxide, and cyanide, the substrates sulfite and nitrite, the intermediate nitric oxide, the product sulfide (or, most likely, an oxidized derivative thereof), and an oxidized nitrogen species (probably nitrate). A hydrogen-bonded cage of ligand-binding arginine and lysine side chains, ordered water molecules, and siroheme carboxylates provides preferred locations for recognizing the common functional groups of these ligands and accommodates their varied sizes, shapes, and charged without requiring substantial structural changes. The coordination geometries presented here suggest that the successively deoxygenated sulfur and nitrogen species produced during catalysis need not alter their orientation in the active site to adopt new stable coordination states. Strong pi-acid ligands decrease the bond length between the siroheme and the proximal cysteine thiolate shared with the iron-sulfur cluster, emphasizing the ability of the coupled cofactors to promote electron tranfer into substrate. On binding the siroheme, the substrate sulfite provides an oxygen atom in a unique location of the binding site compared to all other ligands studied, induces a spin transition in the siroheme iron, flips an active-site arginine, and orders surrounding active-center loops. The loop that coalesces over the active center shields the positively charged ligand-coordinating residues from solvent, enhancing their ability to polarize the substrate. Hydrogen bonds supplied by active-site arginine and lysine residues facilitate charge transfer into the substrate from the electron-rich cofactors, activate S-O bonds for reductive cleavage, and provide potential proton sources for the formation of favorable aquo leaving groups on the substrate. Strong interactions between sulfite and ordered water molecules also implicate solvent as a source of protons for generating product water. From the structures reported here, we propose a series of key structural states of ligated SiRHP in the catalytic reduction of sulfite to sulfide.

Probing the catalytic mechanism of sulfite reductase by X-ray crystallography: structures of the Escherichia coli hemoprotein in complex with substrates, inhibitors, intermediates, and products.,Crane BR, Siegel LM, Getzoff ED Biochemistry. 1997 Oct 7;36(40):12120-37. PMID:9315849<ref>PMID:9315849</ref>

From MEDLINE&reg;/PubMed&reg;, a database of the U.S. National Library of Medicine.<br>
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== References ==
<references/>
__TOC__
</StructureSection>
[[Category: Escherichia coli B]]
[[Category: Large Structures]]
[[Category: Crane BR]]
[[Category: Getzoff ED]]