Acid-induced activation of the urease promoters is mediated directly by the ArsRS two-component system of Helicobacter pylori

The nickel-containing enzyme urease is an essential colonization factor of the human gastric pathogen Helicobacter pylori which enables the bacteria to survive the low-pH conditions of the stomach. Transcription of the urease genes is positively controlled in response to increasing concentrations of nickel ions and acidic pH. Here we demonstrate that acid-induced transcription of the urease genes is mediated directly by the ArsRS two-component system. Footprint analyses identify binding sites of the phosphorylated ArsR response regulator within the ureA and ureI promoters. Furthermore, deletion of a distal upstream ArsR binding site of the ureA promoter demonstrates its role in acid-dependent activation of the promoter. In addition, acid-induced transcription of the ureA gene is unaltered in a nikR mutant, providing evidence that pH-responsive regulation and nickel-responsive regulation of the ureA promoter are mediated by independent mechanisms involving the ArsR response regulator and the NikR protein.