1SK2

ARSENATE REDUCTASE R60A MUTANT +0.4M ARSENATE FROM E. COLI

Summary for 1SK2

• Entry DOI: 10.2210/pdb1sk2/pdb
• Related: 1S3C 1S3D 1SD8 1SD9 1SJZ 1SK0 1SK1
• Descriptor: Arsenate reductase, SULFATE ION, CESIUM ION, ... (4 entities in total)
• Functional Keywords: arsc, reductase, arsenite, arsenate, oxidoreductase
• Biological source: Escherichia coli
• Total number of polymer chains: 1
• Total formula weight: 16453.76

Authors

DeMel, S.,Edwards, B.F. (deposition date: 2004-03-04, release date: 2005-02-15, Last modification date: 2024-04-03)

Primary citation

DeMel, S.,Shi, J.,Martin, P.,Rosen, B.P.,Edwards, B.F.
Arginine 60 in the ArsC arsenate reductase of E. coli plasmid R773 determines the chemical nature of the bound As(III) product.
Protein Sci., 13:2330-2340, 2004

PubMed Abstract: 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.

PubMed: 15295115
DOI: 10.1110/ps.04787204

Experimental method

X-RAY DIFFRACTION (1.54 Å)