The unique glutathione reductase from Xanthomonas campestris: gene expression and enzyme characterization.
The glutathione reductase gene, gor, was cloned from the plant pathogen Xanthomonas campestris pv. phaseoli. Its gene expression and enzyme characteristics were found to be different from those of previously studied homologues. Northern blot hybridization, promoter-lacZ fusion, and enzyme assay experiments revealed that its expression, unlike in Escherichia coli, is OxyR-independent and constitutive upon oxidative stress conditions. The deduced amino acid sequence shows a unique NADPH binding motif where the most highly conserved arginine residue, which is critical for NADPH binding, is replaced by glutamine. Interestingly, a search of the available Gor amino acid sequences from various sources, including other Xanthomonas species, revealed that this replacement is specific to the genus Xanthomonas. Recombinant Gor enzyme was purified and characterized, and was found to have a novel ability to use both, NADPH and NADH, as electron donor. A gor knockout mutant was constructed and shown to have increased expression of the organic peroxide-inducible regulator gene, ohrR.
Loprasert
Suvit
S
Laboratory of Biotechnology, Chulabhorn Research Institute, Lak Si, Bangkok 10210, Thailand. suvit@cri.or.th
Whangsuk
Wirongrong
W
Sallabhan
Ratiboot
R
Mongkolsuk
Skorn
S
D000595:Amino Acid Sequence; D001483:Base Sequence; D001665:Binding Sites; D003001:Cloning, Molecular; D004269:DNA, Bacterial; D004591:Electrophoresis, Polyacrylamide Gel; D015971:Gene Expression Regulation, Enzymologic; D005980:Glutathione Reductase / Q000235:genetics / Q000378:metabolism*; D007700:Kinetics; D008969:Molecular Sequence Data; D008970:Molecular Weight; D016959:Xanthomonas campestris / Q000201:enzymology*
D004269:DNA, Bacterial; D005980:Glutathione Reductase