A 26 kDa protein of Helicobacter pylori shows alkyl hydroperoxide reductase (AhpC) activity and the mono-cistronic transcription of the gene is affected by pH

The 26 kDa protein of Helicobacter pylori, with 67% amino acid identity to alkyl hydroperoxide reductase (AhpC) of Campylobacter jejuni, was studied. We wanted to evaluate it the protein has AhpC activity. Therefore, an Esche richia coli mutant defective for alkyl hydroperoxide reductase and a plasmi d expressing the 26 kDa protein from H. pylori were used in complementation studies. The complemented E. coli mutant showed a decreased sensitivity to cumene hydroperoxide indicating that the 26 kDa protein of H. pylori has A hpC activity and could be of importance in the defence against oxidative st ress. Furthermore, Northern blot analysis detected one mRNA transcript of a pproximately 700 bp which is in agreement with the gene being transcribed a s a single gene with its own promoter. This promoter region was further cha racterized by primer extension experiments. Additional studies on how envir onmental factors, such as long term growth and pH, can affect the transcrip tion of the gene were performed on two H. pylori strains. We found that low pH and long term growth repressed transcription of the gene. Attempts to c onstruct a mutant deficient for the gene in H. pylori were unsuccessful. (C ) 2000 Academic Press.