Crystal Structures and Reaction Mechanism of 1-Cys Peroxiredoxin from Vibrio vulnificus

Abstract

Vibrio vulnificus is capable of causing severe food-borne and often fatal wound infections. It causes two distinct disease syndromes, life-threatening septicemia and necrotizing wound infections. Under reactive oxygen species (ROS) and reactive nitrogen species (RNS) stress, pathogens have evolved elaborate strategies to survival against to host defense systems. Peroxiredoxins (Prxs) are the ubiquitous cysteine-based peroxidase enzymes. Recently, a new type of Prx, called VvPrx3, was identified in V. vulnificus as an essential gene for survival of the bacterium in a mouse model. It belongs to 1-Cys Prx family proteins that contain only one catalytic cysteine residue. Interestingly, VvPrx3 was induced by the transcriptional factor, IscR, different from other types of Prx in V. vulnificus. In this study, I determine the crystal structures of VvPrx3 from V. vulnificus both in the reduced and the oxidized forms at high resolutions. The crystal structure in the reduced form showed a typical dimeric interface, previously characterized as A-type interface. The oxidized structure revealed a novel oligomeric interface, which is mediated by a disulfide bond between the catalytic cysteine residues. Ensuing biochemical studies showed that this disulfide was induced by treatment of peroxides and NO. The oligomeric state of Prx3, which was shown in the crystal structure, was confirmed by analytic size exclusion chromatography. I also found that a reductase Grx3 can efficiently reduce the intermolecular disulfide of VvPrx3. Taken together, I propose a novel function of 1-Cys peroxiredoxin in direct scavenging of peroxides and NO stresses via a novel type of oligomerization, and these findings would help understand diverse functions of peroxiredoxins during pathogenic process at the molecular level. It may further contribute to development of drugs or food sanitizers to cope with the food-borne diseases caused by Vibrio vulnificus by controlling the Prx3 functions based on the structure of Prx3.