Characterization of the Vibrio vulnificus 1-Cys peroxiredoxin Prx3 and regulation of its expression by the Fe-S cluster regulator IscR in response to oxidative stress and iron starvation.
Peroxiredoxins (Prxs) are ubiquitous antioxidant enzymes that reduce toxic peroxides. A new Vibrio vulnificus Prx, named Prx3, was identified and characterized in this study. Biochemical and mutational analyses revealed that Prx3 reduces H2O2, utilizing glutaredoxin 3 (Grx3) and glutathione (GSH) as reductants, and requires only N-terminal peroxidatic cysteine for its catalysis. These results, combined with the monomeric size of Prx3 observed under non-reducing conditions, suggested that Prx3 is a Grx3/GSH-dependent 1-Cys Prx and oxidized without forming intermolecular disulfide bonds. The prx3 mutation impaired growth in the medium containing peroxides and reduced virulence in mice, indicating that Prx3 is essential for survival under oxidative stress and pathogenesis of V. vulnificus. The Fe-S cluster regulator IscR activates prx3 by direct binding to a specific binding sequence centered at -44 from the transcription start site. The binding sequence was homologous to the Type 2 IscR-binding sequence, most likely recognized by the Fe-S clusterless apo-IscR in Escherichia coli. The iscR3CA mutant, chromosomally encoding the apo-locked IscR, exhibited 3-fold higher levels of activation of prx3 than the wild type and accumulated more IscR3CA protein in cells. The IscR-dependent activation of prx3 by aerobic growth and iron starvation was also associated with the increase in cellular levels of IscR protein. Taken together, the results suggested that IscR senses iron starvation as well as reactive oxygen species and shifts to the apo-form, which leads to the increase of cellular IscR and in turn prx3 expression, contributing to the survival and virulence of V. vulnificus during pathogenesis.
From the National Research Laboratory of Molecular Microbiology and Toxicology, Department of Agricultural Biotechnology, Center for Food Safety and Toxicology, Seoul National University, Seoul 151-921, South Korea.
Jong Gyu
JG
Lim
From the National Research Laboratory of Molecular Microbiology and Toxicology, Department of Agricultural Biotechnology, Center for Food Safety and Toxicology, Seoul National University, Seoul 151-921, South Korea.
Ye-Ji
YJ
Bang
From the National Research Laboratory of Molecular Microbiology and Toxicology, Department of Agricultural Biotechnology, Center for Food Safety and Toxicology, Seoul National University, Seoul 151-921, South Korea choish@snu.ac.kr.
Sang Ho
SH
Choi
D000595:Amino Acid Sequence; D000818:Animals; D001426:Bacterial Proteins / Q000737:chemistry / Q000502:physiology*; D001483:Base Sequence; D001665:Binding Sites; D005260:Female; D015964:Gene Expression Regulation, Bacterial; D007501:Iron / Q000378:metabolism; D008813:Mice, Inbred ICR; D050296:Microbial Viability; D008969:Molecular Sequence Data; D018384:Oxidative Stress; D061105:Peroxiredoxin III / Q000737:chemistry / Q000502:physiology*; D011401:Promoter Regions, Genetic; D014158:Transcription, Genetic; D014735:Vibrio Infections / Q000382:microbiology; D041261:Vibrio vulnificus / Q000201:enzymology* / Q000472:pathogenicity; D014774:Virulence
D001426:Bacterial Proteins; D007501:Iron; D061105:Peroxiredoxin III
Bacterial Pathogenesis; Gene Regulation; Iron Starvation; IscR; Oxidative Stress; Peroxiredoxin; Reactive Oxygen Species (ROS); Vibrio vulnificus