Regulation of expression of atypical orphan response regulators of Helicobacter pylori.

The human gastric pathogen Helicobacter pylori exhibits a remarkably small repertoire of transcriptional regulators including three complete two-component systems as well as the orphan response regulators HP1021 and HP1043. Both HP1021 and HP1043 show atypical receiver sequences and are required for the normal cell growth of H. pylori. Recently, we demonstrated that phosphorylation of HP1021 and HP1043 according to the two-component paradigm is not a prerequisite for the cell growth-associated functions of these response regulators, raising the question of how the activity of this regulatory proteins is modulated. Here, we report that strict transcriptional control of its expression is not involved in the cell-growth associated function of HP1021. We show that expression of hp1043 is controlled both on the post-transcriptional or post-translational level and by transcriptional regulation. Furthermore, we provide evidence that hp1043 can be replaced by the orthologous gene cj0355 from Campylobacter jejuni.