1ulx: Difference between revisions
New page: left|200px<br /><applet load="1ulx" size="450" color="white" frame="true" align="right" spinBox="true" caption="1ulx, resolution 2.00Å" /> '''Partially photolyzed... |
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[[Image:1ulx.gif|left|200px]]<br /><applet load="1ulx" size=" | [[Image:1ulx.gif|left|200px]]<br /><applet load="1ulx" size="350" color="white" frame="true" align="right" spinBox="true" | ||
caption="1ulx, resolution 2.00Å" /> | caption="1ulx, resolution 2.00Å" /> | ||
'''Partially photolyzed structure of CO-bound heme-heme oxygenase complex'''<br /> | '''Partially photolyzed structure of CO-bound heme-heme oxygenase complex'''<br /> | ||
==Overview== | ==Overview== | ||
Heme oxygenase (HO) catalyzes physiological heme degradation using O(2) | Heme oxygenase (HO) catalyzes physiological heme degradation using O(2) and reducing equivalents to produce biliverdin, iron, and CO. Notably, the HO reaction proceeds without product inhibition by CO, which is generated in the conversion reaction of alpha-hydroxyheme to verdoheme, although CO is known to be a potent inhibitor of HO and other heme proteins. In order to probe how endogenous CO is released from the reaction site, we collected X-ray diffraction data from a crystal of the CO-bound form of the ferrous heme-HO complex in the dark and under illumination by a red laser at approximately 35 K. The difference Fourier map indicates that the CO ligand is partially photodissociated from the heme and that the photolyzed CO is trapped in a hydrophobic cavity adjacent to the heme pocket. This hydrophobic cavity was occupied also by xenon, which is similar to CO in terms of size and properties. Taking account of the affinity of CO for the ferrous verdoheme-HO complex being much weaker than that for the ferrous heme complex, the CO derived from alpha-hydroxyheme would be trapped preferentially in the hydrophobic cavity but not coordinated to the iron of verdoheme. This structural device would ensure the smooth progression of the subsequent reaction, from verdoheme to biliverdin, which requires O(2) binding to verdoheme. | ||
==About this Structure== | ==About this Structure== | ||
1ULX is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Rattus_norvegicus Rattus norvegicus] with HEM and CMO as [http://en.wikipedia.org/wiki/ligands ligands]. Active as [http://en.wikipedia.org/wiki/Heme_oxygenase Heme oxygenase], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=1.14.99.3 1.14.99.3] Full crystallographic information is available from [http:// | 1ULX is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Rattus_norvegicus Rattus norvegicus] with <scene name='pdbligand=HEM:'>HEM</scene> and <scene name='pdbligand=CMO:'>CMO</scene> as [http://en.wikipedia.org/wiki/ligands ligands]. Active as [http://en.wikipedia.org/wiki/Heme_oxygenase Heme oxygenase], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=1.14.99.3 1.14.99.3] Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=1ULX OCA]. | ||
==Reference== | ==Reference== | ||
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[[Category: photolyzed intermediate]] | [[Category: photolyzed intermediate]] | ||
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Revision as of 16:26, 21 February 2008
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Partially photolyzed structure of CO-bound heme-heme oxygenase complex
OverviewOverview
Heme oxygenase (HO) catalyzes physiological heme degradation using O(2) and reducing equivalents to produce biliverdin, iron, and CO. Notably, the HO reaction proceeds without product inhibition by CO, which is generated in the conversion reaction of alpha-hydroxyheme to verdoheme, although CO is known to be a potent inhibitor of HO and other heme proteins. In order to probe how endogenous CO is released from the reaction site, we collected X-ray diffraction data from a crystal of the CO-bound form of the ferrous heme-HO complex in the dark and under illumination by a red laser at approximately 35 K. The difference Fourier map indicates that the CO ligand is partially photodissociated from the heme and that the photolyzed CO is trapped in a hydrophobic cavity adjacent to the heme pocket. This hydrophobic cavity was occupied also by xenon, which is similar to CO in terms of size and properties. Taking account of the affinity of CO for the ferrous verdoheme-HO complex being much weaker than that for the ferrous heme complex, the CO derived from alpha-hydroxyheme would be trapped preferentially in the hydrophobic cavity but not coordinated to the iron of verdoheme. This structural device would ensure the smooth progression of the subsequent reaction, from verdoheme to biliverdin, which requires O(2) binding to verdoheme.
About this StructureAbout this Structure
1ULX is a Single protein structure of sequence from Rattus norvegicus with and as ligands. Active as Heme oxygenase, with EC number 1.14.99.3 Full crystallographic information is available from OCA.
ReferenceReference
CO-trapping site in heme oxygenase revealed by photolysis of its co-bound heme complex: mechanism of escaping from product inhibition., Sugishima M, Sakamoto H, Noguchi M, Fukuyama K, J Mol Biol. 2004 Jul 30;341(1):7-13. PMID:15312758
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