Distinct characteristics of OxyR2, a new OxyR-type regulator, ensuring expression of Peroxiredoxin 2 detoxifying low levels of hydrogen peroxide in Vibrio vulnificus.

PEROXIREDOXINS; HYDROGEN peroxide; VIBRIO vulnificus; GENETIC regulation; GENETIC transcription; GENE expression

Two peroxiredoxins, Prx1 and Prx2, were previously identified in Vibrio vulnificus. Besides OxyR1, a homologue of E scherichia coli OxyR ( EcOxyR), OxyR2 that shares low homology with EcOxyR was first identified in V . vulnificus. OxyR2 activated prx2 during aerobic growth, while OxyR1 activated prx1 only when exposed to exogenous H2O2. OxyR2 was oxidized to form a reversible C206 to C215 disulphide bond by sensing low levels of H2O2, which were insufficient to oxidize OxyR1, and only the oxidized OxyR2 activated prx2. OxyR25 CA, in which all cysteine residues except for C206 and C215 were replaced with alanines, and its mutants, OxyR25 CA- C206 S and OxyR25 CA- C215 S, were constructed. OxyR25 CA and OxyR25 CA- C215 S directly bound to a specific binding sequence centred at −56.5 from the prx2 transcription start site, albeit with different binding affinities. The binding sequence consisted of four ATCGnt elements spaced by a helical turn and aligned in the twofold dyad symmetry, suggesting that OxyR2 binds DNA as a tetramer. OxyR25 CA- C206 S also directly bound to DNA comprising more extended sequences, indicating that oxidized and reduced OxyR2 adopt different conformational states, leading to altered DNA contacts. The oxyR2 mutation reduced cytotoxicity and growth during infection, indicating that OxyR2 is essential for the pathogenesis of V . vulnificus. [ABSTRACT FROM AUTHOR]