Contribution of the Helicobacter pylori Thiol Peroxidase Bacterioferritin Comigratory Protein to Oxidative Stress Resistance and Host Colonization

Abstract

Peroxiredoxins, the enzymes that catalyze the reduction of hydrogen peroxide and organic hydroperoxides, are ubiquitous proteins that protect organisms from damage by reactive oxygen species. Helicobacter pylori contains three members of the peroxiredoxin family: AhpC (alkyl hydroperoxide reductase), Tpx (thiol-specific peroxidase), and bacterioferritin comigratory protein (BCP). In this study, we characterized H. pylori bcp mutant strains and wild-type BCP. Compared to the parent strain and the ahpC mutant strain, the bcp mutant showed moderate sensitivity to the superoxide-generating agent paraquat and to organic hydroperoxides. Upon exposure of 10 8 cells to air for 10 h, 10 6 wild-type cells survived but none of the 10 8 bcp mutant cells were recovered. Introduction of an intact bcp gene at an unrelated locus in the bcp strain restored the wild-type-like oxidative stress resistance phenotype. Purified BCP was shown to be a thiol peroxidase that depends on the reducing activity of thioredoxin and thioredoxin reductase. Among a series of peroxides tested, linoleic acid hydroperoxide was the preferred substrate of BCP. By examining the profiles of protein expression within H. pylori cells, we confirmed that AhpC is much more abundant than BCP. The overlapping functions and activities of BCP and AhpC probably explain why the bcp mutant displayed a relatively weak oxidative stress resistance phenotype. The bcp mutant strain could colonize mouse stomachs, although colonization by the wild-type strain was slightly better than that by the mutant strain at 1 week after host inoculation. However, at 3 weeks after inoculation, the colonization ability of the wild type was significantly greater than that of the bcp mutant; for example, H. pylori was recovered from 10 of 11 mouse stomachs inoculated with the wild-type strain but from only 4 of 12 mice that were inoculated with the bcp mutant strain. This indicates that H. pylori BCP plays a significant role in efficient host colonization.

The antioxidant protein alkylhydroperoxide reductase of Helicobacter pylori switches from a peroxide reductase to a molecular chaperone function

“…Several functional studies of H. pylori AhpC have shown that the AhpCdeleted mutants have increased sensitivity to oxygen (15), overexpress neutrophil-activating protein (18), and accelerate inactivation of catalase (25). As a member of 2-Cys peroxiredoxins (17,21,31), AhpC has been shown to be Trx-dependent (17,27,32,33). The native structure of AhpC in S. typhimurium was shown to exist as a dimer (34,35).…”

Mutation of cytotoxin-associated gene A affects expressions of antioxidant proteins of Helicobacter pylori

“…Alkyl hydroperoxide reductase (AhpC), a thioredoxin (Trx)-dependent AhpC, is a member of the 2-Cys peroxiredoxins family (2-Cys Prxs). A group of thiolspecific antioxidant enzymes, which catalyze the reduction of hydrogen peroxide and organic hydroperoxides, are ubiquitous proteins that protect organisms from damage by reactive oxygen species [15] . H pylori are oxygensensitive microaerophilic bacteria, and contain many antioxidant proteins, among which AhpC is most abundant.…”

Helicobacter pyloridefense against oxidative attack

“…The structure of the binding site of E. coli Tpx appears to be optimized for recognition of fatty acid hydroperoxides (22), suggesting that this is a major function of the enzyme. The three Prxs of H. pylori have different substrate preferences: AhpC and Hp-Tpx exhibit broad protective activity against a range of hydroperoxides (9,26), and Bcp has a distinct substrate preference for linoleic acid (103). AhpC from H. pylori and other bacterial species also possess activity against peroxynitrite, which has not been observed for the other enzymes (15).…”

“…AhpC from H. pylori and other bacterial species also possess activity against peroxynitrite, which has not been observed for the other enzymes (15). The enzymes are distinguished by the number of conserved cysteine residues within the structure, with AhpC classified as a "typical" 2-Cys Prx (78), Hp-Tpx as an "atypical" 2-Cys Prx (70), and Bcp as a 1-Cys Prx (103). Typical and atypical 2-Cys Prxs differ in the conformation of the disulfide bond that forms upon oxidation of the cysteine residues: the disulfide bond of typical 2-Cys Prx is intermolecular, leading to dimer formation, whereas the bond in atypical 2-Cys Prx is intramolecular, resulting in monomer formation (83).…”