1sd9: Difference between revisions
New page: left|200px<br /><applet load="1sd9" size="450" color="white" frame="true" align="right" spinBox="true" caption="1sd9, resolution 1.65Å" /> '''ARSENATE REDUCTASE C... |
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[[Image:1sd9.gif|left|200px]]<br /><applet load="1sd9" size=" | [[Image:1sd9.gif|left|200px]]<br /><applet load="1sd9" size="350" color="white" frame="true" align="right" spinBox="true" | ||
caption="1sd9, resolution 1.65Å" /> | caption="1sd9, resolution 1.65Å" /> | ||
'''ARSENATE REDUCTASE C12S MUTANT +0.4M ARSENATE FROM E. COLI'''<br /> | '''ARSENATE REDUCTASE C12S MUTANT +0.4M ARSENATE FROM E. COLI'''<br /> | ||
==Overview== | ==Overview== | ||
Arsenic is a ubiquitous environmental toxic metal. Consequently, organisms | Arsenic is a ubiquitous environmental toxic metal. Consequently, organisms detoxify arsenate by reduction to arsenite, which is then excreted or sequestered. The ArsC arsenate reductase from Escherichia coli plasmid R773, the best characterized arsenic-modifying enzyme, has a catalytic cysteine, Cys 12, in the active site, surrounded by an arginine triad composed of Arg 60, Arg 94, and Arg 107. During the reaction cycle, the native enzyme forms a unique monohydroxyl Cys 12-thiol-arsenite adduct that contains a positive charge on the arsenic. We hypothesized previously that this unstable intermediate allows for rapid dissociation of the product arsenite. In this study, the role of Arg 60 in product formation was evaluated by mutagenesis. A total of eight new structures of ArsC were determined at resolutions between 1.3 A and 1.8 A, with R(free) values between 0.18 and 0.25. The crystal structures of R60K and R60A ArsC equilibrated with the product arsenite revealed a covalently bound Cys 12-thiol-dihydroxyarsenite without a charge on the arsenic atom. We propose that this intermediate is more stable than the monohydroxyarsenite intermediate of the native enzyme, resulting in slow release of product and, consequently, loss of activity. | ||
==About this Structure== | ==About this Structure== | ||
1SD9 is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Escherichia_coli Escherichia coli] with SO4 and CS as [http://en.wikipedia.org/wiki/ligands ligands]. Active as [http://en.wikipedia.org/wiki/Arsenate_reductase_(glutaredoxin) Arsenate reductase (glutaredoxin)], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=1.20.4.1 1.20.4.1] Full crystallographic information is available from [http:// | 1SD9 is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Escherichia_coli Escherichia coli] with <scene name='pdbligand=SO4:'>SO4</scene> and <scene name='pdbligand=CS:'>CS</scene> as [http://en.wikipedia.org/wiki/ligands ligands]. Active as [http://en.wikipedia.org/wiki/Arsenate_reductase_(glutaredoxin) Arsenate reductase (glutaredoxin)], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=1.20.4.1 1.20.4.1] Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=1SD9 OCA]. | ||
==Reference== | ==Reference== | ||
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[[Category: Single protein]] | [[Category: Single protein]] | ||
[[Category: DeMel, S.]] | [[Category: DeMel, S.]] | ||
[[Category: Edwards, B | [[Category: Edwards, B F.]] | ||
[[Category: CS]] | [[Category: CS]] | ||
[[Category: SO4]] | [[Category: SO4]] | ||
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[[Category: reductase]] | [[Category: reductase]] | ||
''Page seeded by [http:// | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Thu Feb 21 15:00:19 2008'' | ||
Revision as of 16:00, 21 February 2008
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ARSENATE REDUCTASE C12S MUTANT +0.4M ARSENATE FROM E. COLI
OverviewOverview
Arsenic is a ubiquitous environmental toxic metal. Consequently, organisms detoxify arsenate by reduction to arsenite, which is then excreted or sequestered. The ArsC arsenate reductase from Escherichia coli plasmid R773, the best characterized arsenic-modifying enzyme, has a catalytic cysteine, Cys 12, in the active site, surrounded by an arginine triad composed of Arg 60, Arg 94, and Arg 107. During the reaction cycle, the native enzyme forms a unique monohydroxyl Cys 12-thiol-arsenite adduct that contains a positive charge on the arsenic. We hypothesized previously that this unstable intermediate allows for rapid dissociation of the product arsenite. In this study, the role of Arg 60 in product formation was evaluated by mutagenesis. A total of eight new structures of ArsC were determined at resolutions between 1.3 A and 1.8 A, with R(free) values between 0.18 and 0.25. The crystal structures of R60K and R60A ArsC equilibrated with the product arsenite revealed a covalently bound Cys 12-thiol-dihydroxyarsenite without a charge on the arsenic atom. We propose that this intermediate is more stable than the monohydroxyarsenite intermediate of the native enzyme, resulting in slow release of product and, consequently, loss of activity.
About this StructureAbout this Structure
1SD9 is a Single protein structure of sequence from Escherichia coli with and as ligands. Active as Arsenate reductase (glutaredoxin), with EC number 1.20.4.1 Full crystallographic information is available from OCA.
ReferenceReference
Arginine 60 in the ArsC arsenate reductase of E. coli plasmid R773 determines the chemical nature of the bound As(III) product., DeMel S, Shi J, Martin P, Rosen BP, Edwards BF, Protein Sci. 2004 Sep;13(9):2330-40. Epub 2004 Aug 4. PMID:15295115
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