2e80: Difference between revisions

Revision as of 18:07, 21 February 2008

Cytochrome c Nitrite Reductase from Wolinella succinogenes with bound substrate nitrite

OverviewOverview

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 StructureAbout this Structure

2E80 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.

ReferenceReference

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

Page seeded by OCA on Thu Feb 21 17:07:07 2008

Proteopedia Page Contributors and Editors (what is this?)Proteopedia Page Contributors and Editors (what is this?)

OCA

@@ Line 1: / Line 1: @@
-[[Image:2e80.jpg|left|200px]]<br /><applet load="2e80" size="450" color="white" frame="true" align="right" spinBox="true"
+[[Image:2e80.jpg|left|200px]]<br /><applet load="2e80" size="350" color="white" frame="true" align="right" spinBox="true"
 caption="2e80, resolution 1.6&Aring;" />
 '''Cytochrome c Nitrite Reductase from Wolinella succinogenes with bound substrate nitrite'''<br />
 ==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.
+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==
-E80 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 NO2, ACT, CA, YT3 and HEM 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://ispc.weizmann.ac.il/oca-bin/ocashort?id=2E80 OCA].
+E80 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=NO2:'>NO2</scene>, <scene name='pdbligand=ACT:'>ACT</scene>, <scene name='pdbligand=CA:'>CA</scene>, <scene name='pdbligand=YT3:'>YT3</scene> and <scene name='pdbligand=HEM:'>HEM</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=2E80 OCA].
 ==Reference==
@@ Line 15: / Line 15: @@
 [[Category: Wolinella succinogenes]]
 [[Category: Einsle, O.]]
-[[Category: Kroneck, P.M.H.]]
+[[Category: Kroneck, P M.H.]]
 [[Category: ACT]]
 [[Category: CA]]
@@ Line 25: / Line 25: @@
 [[Category: substrate complex]]
-''Page seeded by [http://ispc.weizmann.ac.il/oca OCA ] on Wed Nov 21 09:59:18 2007''
+''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Thu Feb 21 17:07:07 2008''