A New Antioxidant with Dual Functions as a Peroxidase and Chaperone in Pseudomonas aeruginosa

Abstract

Thiol-based peroxiredoxins (Prxs) are conserved throughout all kingdoms. We have found that a conserved typical 2-Cys Prx-like protein (PaPrx) from Pseudomonas aeruginosa bacteria displays diversity in its structure and apparent molecular weight (MW), and can act alternatively as a peroxidase and molecular chaperone. We have also identified a regulatory factor involved in this structural and functional switching. Exposure of P. aeruginosa to hydrogen peroxide (H2O2) causes PaPrx to convert from a high MW (HMW) complex to a low MW (LMW) form, which triggers a chaperone to peroxidase functional switch. This structural switching is primarily guided by either the thioredoxin (Trx) or glutathione (GSH) systems. Furthermore, comparison of our structural data [native and non-reducing polyacrylamide gel electrophoresis (PAGE) analysis, size exclusion chromatography (SEC) analysis, and electron microscopy (EM) observations] and enzymatic analyses (peroxidase and chaperone assay) revealed that the formation of oligomeric HMW complex structures increased chaperone activity of PaPrx. These results suggest that multimerization of PaPrx complexes promotes chaperone activity, and dissociation of the complexes into LMW species enhances peroxidase activity. Thus, the dual functions of PaPrx are clearly associated with their ability to form distinct protein structures.

Pseudomonas aeruginosa Thiol Peroxidase Protects against Hydrogen Peroxide Toxicity and Displays Atypical Patterns of Gene Regulation

“…In general, P. aeruginosa has redundant systems to scavenge H 2 O 2 generated within cells or from exogenous sources. It produces several isozymes of catalases and peroxiredoxins that are capable of degrading H 2 O 2 (2,24,39,42). Total catalase activity in the ⌬tpx mutant and in the parental PAO1 wild type were measured to test whether the H 2 O 2 -sensitive phenotype of the ⌬tpx mutant arose from changes in the total catalase activity levels.…”

“…A number of ROS-scavenging enzymes have been reported to play a physiological role in oxidative stress protection. P. aeruginosa produces several isozymes of superoxide dismutases to dismutate superoxide anions, catalases to detoxify H 2 O 2 , and peroxiredoxins to detoxify peroxides, including both organic hydroperoxides and H 2 O 2 (2,6,24,25,39,41,42). Here, we report the biochemical, genetic, and physiological characterization of tpx and reveal it to be an important member of a group of peroxide removal genes that protect P. aeruginosa from oxidative stress.…”

Engineering of 2-Cys Peroxiredoxin for Enhanced Stress-Tolerance

“…Based on the enzymatic analysis results, this PpPrx has dual functions as a dominant chaperone and a recessive peroxidase activity (An et al, 2011). The PaPrx protein from P. aeruginosa PAO1 also contains 200 amino acids, and has dual functions as a dominant peroxidase and a recessive chaperone (An et al, 2010). In the present study, PaPrx and PpPrx were aligned, revealing a sequence homology of 93%.…”

“…Oxidized Cys P is attacked by the resolving Cys (Cys R ). Two oxidized active Cys residues are formed via intra-or intermolecular disulfide bonds after yielding water or the corresponding alcohol (An et al, 2010;2011;Dietz, 2003;Hofmann et al, 2002).…”

“…Prxs can act either as peroxidases or as molecular chaperones, with reversible switching between the dual enzymatic functions (An et al, 2010;2011;Chuang et al, 2006;Jang et al, 2004;2006a). These properties enable Prxs to prevent the stress-induced misfolding or aggregation of intracellular macromolecules (Chuang et al, 2006;Jang et al, 2004;2006a).…”