1sjz
ARSENATE REDUCTASE R60K MUTANT +0.4M ARSENITE FROM E. COLI
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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
1SJZ is a Single protein structure of sequence from Escherichia coli with SO4, CS and TAS 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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