2e81
From Proteopedia
(New page: 200px<br /><applet load="2e81" size="450" color="white" frame="true" align="right" spinBox="true" caption="2e81, resolution 2.0Å" /> '''Cytochrome c Nitrite ...) |
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| - | [[Image:2e81.jpg|left|200px]]<br /><applet load="2e81" size=" | + | [[Image:2e81.jpg|left|200px]]<br /><applet load="2e81" size="350" color="white" frame="true" align="right" spinBox="true" |
caption="2e81, resolution 2.0Å" /> | caption="2e81, resolution 2.0Å" /> | ||
'''Cytochrome c Nitrite Reductase from Wolinella succinogenes with bound intermediate hydroxylamine'''<br /> | '''Cytochrome c Nitrite Reductase from Wolinella succinogenes with bound intermediate hydroxylamine'''<br /> | ||
==Overview== | ==Overview== | ||
| - | Cytochrome c nitrite reductase catalyzes the six-electron reduction of | + | Cytochrome c nitrite reductase catalyzes the six-electron reduction of nitrite to ammonia without the release of potential reaction intermediates, such as NO or hydroxylamine. On the basis of the crystallographic observation of reaction intermediates and of density functional calculations, we present a working hypothesis for the reaction mechanism of this multiheme enzyme which carries a novel lysine-coordinated heme group (Fe-Lys). It is proposed that nitrite reduction starts with a heterolytic cleavage of the N-O bond which is facilitated by a pronounced back-bonding interaction of nitrite coordinated through nitrogen to the reduced (Fe(II)) but not the oxidized (Fe(III)) active site iron. This step leads to the formation of an [FeNO](6) species and a water molecule and is further facilitated by a hydrogen bonding network that induces an electronic asymmetry in the nitrite molecule that weakens one N-O bond and strengthens the other. Subsequently, two rapid one-electron reductions lead to an [FeNO](8) form and, by protonation, to an Fe(II)-HNO adduct. Hereafter, hydroxylamine will be formed by a consecutive two-electron two-proton step which is dehydrated in the final two-electron reduction step to give ammonia and an additional water molecule. A single electron reduction of the active site closes the catalytic cycle. |
==About this Structure== | ==About this Structure== | ||
| - | 2E81 is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Wolinella_succinogenes Wolinella succinogenes] with CA, YT3, HEM and HOA as [http://en.wikipedia.org/wiki/ligands ligands]. Active as [http://en.wikipedia.org/wiki/Nitrite_reductase_(cytochrome;_ammonia-forming) Nitrite reductase (cytochrome; ammonia-forming)], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=1.7.2.2 1.7.2.2] Full crystallographic information is available from [http:// | + | 2E81 is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Wolinella_succinogenes Wolinella succinogenes] with <scene name='pdbligand=CA:'>CA</scene>, <scene name='pdbligand=YT3:'>YT3</scene>, <scene name='pdbligand=HEM:'>HEM</scene> and <scene name='pdbligand=HOA:'>HOA</scene> as [http://en.wikipedia.org/wiki/ligands ligands]. Active as [http://en.wikipedia.org/wiki/Nitrite_reductase_(cytochrome;_ammonia-forming) Nitrite reductase (cytochrome; ammonia-forming)], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=1.7.2.2 1.7.2.2] Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=2E81 OCA]. |
==Reference== | ==Reference== | ||
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[[Category: Wolinella succinogenes]] | [[Category: Wolinella succinogenes]] | ||
[[Category: Einsle, O.]] | [[Category: Einsle, O.]] | ||
| - | [[Category: Kroneck, P | + | [[Category: Kroneck, P M.H.]] |
[[Category: CA]] | [[Category: CA]] | ||
[[Category: HEM]] | [[Category: HEM]] | ||
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[[Category: reaction intermediate]] | [[Category: reaction intermediate]] | ||
| - | ''Page seeded by [http:// | + | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Thu Feb 21 17:07:07 2008'' |
Revision as of 15:07, 21 February 2008
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Cytochrome c Nitrite Reductase from Wolinella succinogenes with bound intermediate hydroxylamine
Overview
Cytochrome c nitrite reductase catalyzes the six-electron reduction of nitrite to ammonia without the release of potential reaction intermediates, such as NO or hydroxylamine. On the basis of the crystallographic observation of reaction intermediates and of density functional calculations, we present a working hypothesis for the reaction mechanism of this multiheme enzyme which carries a novel lysine-coordinated heme group (Fe-Lys). It is proposed that nitrite reduction starts with a heterolytic cleavage of the N-O bond which is facilitated by a pronounced back-bonding interaction of nitrite coordinated through nitrogen to the reduced (Fe(II)) but not the oxidized (Fe(III)) active site iron. This step leads to the formation of an [FeNO](6) species and a water molecule and is further facilitated by a hydrogen bonding network that induces an electronic asymmetry in the nitrite molecule that weakens one N-O bond and strengthens the other. Subsequently, two rapid one-electron reductions lead to an [FeNO](8) form and, by protonation, to an Fe(II)-HNO adduct. Hereafter, hydroxylamine will be formed by a consecutive two-electron two-proton step which is dehydrated in the final two-electron reduction step to give ammonia and an additional water molecule. A single electron reduction of the active site closes the catalytic cycle.
About this Structure
2E81 is a Single protein structure of sequence from Wolinella succinogenes with , , and as ligands. Active as Nitrite reductase (cytochrome; ammonia-forming), with EC number 1.7.2.2 Full crystallographic information is available from OCA.
Reference
Mechanism of the six-electron reduction of nitrite to ammonia by cytochrome c nitrite reductase., Einsle O, Messerschmidt A, Huber R, Kroneck PM, Neese F, J Am Chem Soc. 2002 Oct 2;124(39):11737-45. PMID:12296741
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