An Arsenate-activated Glutaredoxin from the Arsenic

To elucidate the mechanisms of arsenic resistance in the arsenic hyperaccumulator fern Pteris vittata L., a cDNA for a glutaredoxin (Grx) Pv5–6 was isolated from a frond expression cDNA library based on the ability of the cDNA to increase arsenic resistance in Escherichia coli. The deduced amino acid sequence of Pv5–6 showed high homology with an Arabidopsis chloroplastic Grx and contained two CXXS putative catalytic motifs. Purified recombinant Pv5–6 exhibited glutaredoxin activity that was increased 1.6-fold by 10mM arsenate. Site-spe-cific mutation of Cys67 to Ala67 resulted in the loss of both GRX activity and arsenic resistance. PvGrx5 was expressed in E. coli mutants in which the arsenic resistance genes of the ars operon were deleted (strain AW3110), a deletion of the gene for the ArsC arsenate reductase (strainWC3110), and a strain in which the ars operon was deleted and the gene for the GlpF aquaglyc