title: An alternate pathway of arsenate resistance in E. coli mediated by the glutathione S-transferase GstB.
abstract: Microbial arsenate resistance is known to be conferred by specialized oxidoreductase enzymes termed arsenate reductases. We carried out a genetic selection on media supplemented with sodium arsenate for multicopy genes that can confer growth to E. coli mutant cells lacking the gene for arsenate reductase (E. coli ΔarsC). We found that overexpression of glutathione S-transferase B (GstB) complemented the ΔarsC allele and conferred growth on media containing up to 5 mM sodium arsenate. Interestingly, unlike wild type E. coli arsenate reductase, arsenate resistance via GstB was not dependent on reducing equivalents provided by glutaredoxins or a catalytic cysteine residue. Instead, two arginine residues, which presumably coordinate the arsenate substrate within the electrophilic binding site of GstB, were found to be critical for transferase activity. We provide biochemical evidence that GstB acts to directly reduce arsenate to arsenite with reduced glutathione (GSH) as the electron donor. Our results reveal a pathway for the detoxification of arsenate in bacteria that hinges on a previously undescribed function of a bacterial glutathione S-transferase.
authors.affiliation: Departments of †Chemical Engineering and ‡Biomedical Engineering, and §Molecular Genetics and Microbiology and Institute for Cell and Molecular Biology, University of Texas, Austin, Texas 78712, United States.
authors.forename: Constantine
authors.initials: C
authors.lastname: Chrysostomou
authors.affiliation: Departments of †Chemical Engineering and ‡Biomedical Engineering, and §Molecular Genetics and Microbiology and Institute for Cell and Molecular Biology, University of Texas, Austin, Texas 78712, United States.
authors.forename: Erik M
authors.initials: EM
authors.lastname: Quandt
authors.affiliation: Departments of †Chemical Engineering and ‡Biomedical Engineering, and §Molecular Genetics and Microbiology and Institute for Cell and Molecular Biology, University of Texas, Austin, Texas 78712, United States.
authors.forename: Nicholas M
authors.initials: NM
authors.lastname: Marshall
authors.affiliation: Departments of †Chemical Engineering and ‡Biomedical Engineering, and §Molecular Genetics and Microbiology and Institute for Cell and Molecular Biology, University of Texas, Austin, Texas 78712, United States.
authors.forename: Everett
authors.initials: E
authors.lastname: Stone
authors.affiliation: Departments of †Chemical Engineering and ‡Biomedical Engineering, and §Molecular Genetics and Microbiology and Institute for Cell and Molecular Biology, University of Texas, Austin, Texas 78712, United States.
authors.forename: George
authors.initials: G
authors.lastname: Georgiou
mesh_terms: D053502:Arsenate Reductases / Q000172:deficiency* / Q000235:genetics; D001149:Arsenates / Q000378:metabolism* / Q000633:toxicity; D018053:Arsenites / Q000378:metabolism; D020134:Catalytic Domain; D024881:Drug Resistance, Bacterial; D004926:Escherichia coli / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D017353:Gene Deletion; D015870:Gene Expression; D005816:Genetic Complementation Test; D054477:Glutaredoxins / Q000378:metabolism; D005978:Glutathione / Q000737:chemistry* / Q000378:metabolism; D005982:Glutathione Transferase / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D007700:Kinetics; D008958:Models, Molecular; D010084:Oxidation-Reduction; D010957:Plasmids / Q000737:chemistry / Q000378:metabolism; D011485:Protein Binding; D014169:Transformation, Bacterial
chemical_list: D001149:Arsenates; D018053:Arsenites; D054477:Glutaredoxins; D053502:Arsenate Reductases; D005982:Glutathione Transferase; D005978:Glutathione; C015001:arsenite; C025657:arsenic acid