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Articles by S. H. Chiou
Total Records ( 2 ) for S. H. Chiou
  C. H Huang , I. L Lee , I. J Yeh , J. H Liao , C. L Ni , S. H Wu and S. H. Chiou

Helicobacter pylori is a spiral Gram-negative microaerophilic bacterium. It is unique and distinctive among various bacterial pathogens for its ability to persist in the extreme acidic environment of human stomachs. To address and identify changes in the proteome of H. pylori in response to low pH, we have used a proteomic approach to study the protein expression of H. pylori under neutral (pH 7) and acidic (pH 5) conditions. Global protein-expression profiles of H. pylori under acid stress were analysed by two-dimensional polyacrylamide gel electrophoresis (2-DE) followed by liquid chromatography (LC)-nanoESI-mass spectrometry (MS)/MS and bioinformatics database analysis. Among the proteins differentially expressed under acidic condition, a non-heme iron-containing ferritin of H. pylori (HP-ferritin) was found to be consistently upregulated at pH 5 as compared to pH 7. It was also found that HP-ferritin can switch from an iron-storage protein with ferroxidase activity to a DNA-binding/protection function under in vitro conditions upon exposure to acidic environment. Prokaryotic ferritins, such as non-heme iron-binding HP-ferritin with dual functionality reported herein, may play a significant urease-independent role in the acid adaptation of H. pylori under physiological conditions in vivo.

  C. H Huang , M. H Chuang , Y. H Wu , W. C Chuang , P. J Jhuang and S. H. Chiou

Alkylhydroperoxide reductase (AhpC) is an abundant and important antioxidant protein present in Helicobacter pylori (HP), a spiral Gram-negative microaerophilic bacterium. By sequence alignment and structure comparison, HP-AhpC was found to be more homologous to human peroxiredoxins (hPrx) than to other eubacterial AhpC proteins. Similar to hPrxI, native HP-AhpC existed as a dimer of single subunit, comprising -helix and β-sheet domains with low surface hydrophobicity. AhpC can form high-molecular-weight (HMW) aggregates ranging from 700 to higher than 2,000 kDa under oxidative stress, possessing chaperone activity in the presence of thioredoxin (Trx). Further analysis of peroxide-reductase activities showed that HP-AhpC was more resistant to H2O2 than hPrxI. However, the mechanism of enzyme inactivation to H2O2 appeared to be similar for both HP-AhpC and hPrxI as revealed by native gel electrophoresis followed by proteomic identification using two-dimensional gel electrophoresis (2-DE) and LC-MS/MS. In contrast to T90D-hPrxI mutant with chaperone activity, site-specific mutant T87D-HP-AhpC did not form HMW chaperone complexes. The comparison of these two evolutionarily distant and yet functionally related enzymes may shed some light on the mechanism(s) underlying the evolution and development of the dual functionality in HP-AhpC and hPrxI with similar protein structure.

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