Crystal structure of peroxiredoxin 3 from and its implications for scavenging peroxides and nitric oxide.

Peroxiredoxins (Prxs) are ubiquitous cysteine-based peroxidase enzymes. Recently, a new type of Prx, Prx3, was identified in the pathogenic bacterium as being important for survival in macrophages. It employs only one catalytic cysteine residue to decompose peroxides. Here, crystal structures of Prx3 representing its reduced and oxidized states have been determined, together with an HO-bound structure, at high resolution. The crystal structure representing the reduced Prx3 showed a typical dimeric interface, called the A-type interface. However, Prx3 forms an oligomeric interface mediated by a disulfide bond between two catalytic cysteine residues from two adjacent dimers, which differs from the doughnut-like oligomers that appear in most Prxs. Subsequent biochemical studies showed that this disulfide bond was induced by treatment with nitric oxide (NO) as well as with peroxides. Consistently, NO treatment induced expression of the gene in , and Prx3 was crucial for the survival of bacteria in the presence of NO. Taken together, the function and mechanism of Prx3 in scavenging peroxides and NO stress oligomerization are proposed. These findings contribute to the understanding of the diverse functions of Prxs during pathogenic processes at the molecular level.