1oq4
From Proteopedia
(New page: 200px<br /><applet load="1oq4" size="450" color="white" frame="true" align="right" spinBox="true" caption="1oq4, resolution 2.40Å" /> '''The Crystal Structur...) |
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| - | [[Image:1oq4.jpg|left|200px]]<br /><applet load="1oq4" size=" | + | [[Image:1oq4.jpg|left|200px]]<br /><applet load="1oq4" size="350" color="white" frame="true" align="right" spinBox="true" |
caption="1oq4, resolution 2.40Å" /> | caption="1oq4, resolution 2.40Å" /> | ||
'''The Crystal Structure of the Complex between Stearoyl Acyl Carrier Protein Desaturase from Ricinus Communis (Castor Bean) and Azide.'''<br /> | '''The Crystal Structure of the Complex between Stearoyl Acyl Carrier Protein Desaturase from Ricinus Communis (Castor Bean) and Azide.'''<br /> | ||
==Overview== | ==Overview== | ||
| - | Delta9 stearoyl-acyl carrier protein (ACP) desaturase is a mu-oxo-bridged | + | Delta9 stearoyl-acyl carrier protein (ACP) desaturase is a mu-oxo-bridged di-iron enzyme, which belongs to the structural class I of large helix bundle proteins and that catalyzes the NADPH and O2-dependent formation of a cis-double bond in stearoyl-ACP. The crystal structures of complexes with azide and acetate, respectively, as well as the apoand single-iron forms of Delta9 stearoyl-ACP desaturase from Ricinus communis have been determined. In the azide complex, the ligand forms a mu-1,3-bridge between the two iron ions in the active site, replacing a loosely bound water molecule. The structure of the acetate complex is similar, with acetate bridging the di-iron center in the same orientation with respect to the di-iron center. However, in this complex, the iron ligand Glu196 has changed its coordination mode from bidentate to monodentate, the first crystallographic observation of a carboxylate shift in Delta9 stearoyl-ACP desaturase. The two complexes are proposed to mimic a mu-1,2 peroxo intermediate present during catalytic turnover. There are striking structural similarities between the di-iron center in the Delta9 stearoyl-ACP desaturase-azide complex and in the reduced rubrerythrin-azide complex. This suggests that Delta9 stearoyl-ACP desaturase might catalyze the formation of water from exogenous hydrogen peroxide at a low rate. From the similarity in iron center structure, we propose that the mu-oxo-bridge in oxidized desaturase is bound to the di-iron center as in rubrerythrin and not as reported for the R2 subunit of ribonucleotide reductase and the hydroxylase subunit of methane monooxygenase. The crystal structure of the one-iron depleted desaturase species demonstrates that the affinities for the two iron ions comprising the di-iron center are not equivalent, Fe1 being the higher affinity site and Fe2 being the lower affinity site. |
==About this Structure== | ==About this Structure== | ||
| - | 1OQ4 is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Ricinus_communis Ricinus communis] with FE and AZI as [http://en.wikipedia.org/wiki/ligands ligands]. Active as [http://en.wikipedia.org/wiki/Acyl-[acyl-carrier-protein]_desaturase Acyl-[acyl-carrier-protein] desaturase], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=1.14.19.2 1.14.19.2] Full crystallographic information is available from [http:// | + | 1OQ4 is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Ricinus_communis Ricinus communis] with <scene name='pdbligand=FE:'>FE</scene> and <scene name='pdbligand=AZI:'>AZI</scene> as [http://en.wikipedia.org/wiki/ligands ligands]. Active as [http://en.wikipedia.org/wiki/Acyl-[acyl-carrier-protein]_desaturase Acyl-[acyl-carrier-protein] desaturase], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=1.14.19.2 1.14.19.2] Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=1OQ4 OCA]. |
==Reference== | ==Reference== | ||
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[[Category: Ricinus communis]] | [[Category: Ricinus communis]] | ||
[[Category: Single protein]] | [[Category: Single protein]] | ||
| - | [[Category: Ghoshal, A | + | [[Category: Ghoshal, A K.]] |
[[Category: Lindqvist, Y.]] | [[Category: Lindqvist, Y.]] | ||
[[Category: Moche, M.]] | [[Category: Moche, M.]] | ||
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[[Category: four-helix bundle]] | [[Category: four-helix bundle]] | ||
| - | ''Page seeded by [http:// | + | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Thu Feb 21 14:20:27 2008'' |
Revision as of 12:20, 21 February 2008
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The Crystal Structure of the Complex between Stearoyl Acyl Carrier Protein Desaturase from Ricinus Communis (Castor Bean) and Azide.
Overview
Delta9 stearoyl-acyl carrier protein (ACP) desaturase is a mu-oxo-bridged di-iron enzyme, which belongs to the structural class I of large helix bundle proteins and that catalyzes the NADPH and O2-dependent formation of a cis-double bond in stearoyl-ACP. The crystal structures of complexes with azide and acetate, respectively, as well as the apoand single-iron forms of Delta9 stearoyl-ACP desaturase from Ricinus communis have been determined. In the azide complex, the ligand forms a mu-1,3-bridge between the two iron ions in the active site, replacing a loosely bound water molecule. The structure of the acetate complex is similar, with acetate bridging the di-iron center in the same orientation with respect to the di-iron center. However, in this complex, the iron ligand Glu196 has changed its coordination mode from bidentate to monodentate, the first crystallographic observation of a carboxylate shift in Delta9 stearoyl-ACP desaturase. The two complexes are proposed to mimic a mu-1,2 peroxo intermediate present during catalytic turnover. There are striking structural similarities between the di-iron center in the Delta9 stearoyl-ACP desaturase-azide complex and in the reduced rubrerythrin-azide complex. This suggests that Delta9 stearoyl-ACP desaturase might catalyze the formation of water from exogenous hydrogen peroxide at a low rate. From the similarity in iron center structure, we propose that the mu-oxo-bridge in oxidized desaturase is bound to the di-iron center as in rubrerythrin and not as reported for the R2 subunit of ribonucleotide reductase and the hydroxylase subunit of methane monooxygenase. The crystal structure of the one-iron depleted desaturase species demonstrates that the affinities for the two iron ions comprising the di-iron center are not equivalent, Fe1 being the higher affinity site and Fe2 being the lower affinity site.
About this Structure
1OQ4 is a Single protein structure of sequence from Ricinus communis with and as ligands. Active as [acyl-carrier-protein_desaturase Acyl-[acyl-carrier-protein] desaturase], with EC number 1.14.19.2 Full crystallographic information is available from OCA.
Reference
Azide and acetate complexes plus two iron-depleted crystal structures of the di-iron enzyme delta9 stearoyl-acyl carrier protein desaturase. Implications for oxygen activation and catalytic intermediates., Moche M, Shanklin J, Ghoshal A, Lindqvist Y, J Biol Chem. 2003 Jul 4;278(27):25072-80. Epub 2003 Apr 18. PMID:12704186 [[Category: Acyl-[acyl-carrier-protein] desaturase]]
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