The antioxidant protein alkylhydroperoxide reductase of Helicobacter pylori switches from a peroxide reductase to a molecular chaperone function.
Helicobacter pylori, an oxygen-sensitive microaerophilic bacterium, contains many antioxidant proteins, among which alkylhydroperoxide reductase (AhpC) is the most abundant. The function of AhpC is to protect H. pylori from a hyperoxidative environment by reduction of toxic organic hydroperoxides. We have found that the sequence of AhpC from H. pylori is more homologous to mammalian peroxiredoxins than to eubacterial AhpC. We have also found that the protein structure of AhpC could shift from low-molecular-weight oligomers with peroxide-reductase activity to high-molecular-weight complexes with molecular-chaperone function under oxidative stresses. Time-course study by following the quaternary structural change of AhpC in vivo revealed that this enzyme changes from low-molecular-weight oligomers under normal microaerobic conditions or short-term oxidative shock to high-molecular-weight complexes after severe long-term oxidative stress. This study revealed that AhpC of H. pylori acts as a peroxide reductase in reducing organic hydroperoxides and as a molecular chaperone for prevention of protein misfolding under oxidative stress.
Chuang
Ming-Hong
MH
Institute of Biochemical Sciences, National Taiwan University, Taipei 106, Taiwan.
Wu
Ming-Shiang
MS
Lo
Wan-Lin
WL
Lin
Jaw-Town
JT
Wong
Chi-Huey
CH
Chiou
Shyh-Horng
SH
D000595:Amino Acid Sequence; D000975:Antioxidants / Q000737:chemistry / Q000378:metabolism; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D003001:Cloning, Molecular; D016480:Helicobacter pylori / Q000201:enzymology*; D006861:Hydrogen Peroxide / Q000378:metabolism; D018832:Molecular Chaperones / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D018384:Oxidative Stress; D010544:Peroxidases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D054464:Peroxiredoxins; D017510:Protein Folding; D016415:Sequence Alignment
D000975:Antioxidants; D001426:Bacterial Proteins; D018832:Molecular Chaperones; D006861:Hydrogen Peroxide; D010544:Peroxidases; D054464:Peroxiredoxins; C508531:ahpC protein, Helicobacter pylori