Structural and Functional Analysis of the Helicobacter pylori Response Regulator ArsR

Abstract

The ArsRS two-component system (TCS), comprised of a sensor histidine kinase (HK) ArsS and a response regulator (RR) ArsR, contributes to pH-responsive gene regulation in Helicobacter pylori. In a typical TCS, a specific environmental stimulus triggers the HK to phosphorylate and induce a conformational change in the RR, altering its cellular functions. In order to elucidate structure-function relationships within the ArsRS TCS, we expressed and purified the full-length ArsR protein and its DNA-binding domain (ArsR-DBD), and analyzed the tertiary structure of ArsR-DBD using solution nuclear magnetic resonance (NMR) methods. The structure of ArsR-DBD consists of an N-terminal four-stranded beta-sheet, a helical core, and a C-terminal beta-hairpin. The overall tertiary fold of ArsR-DBD is most closely related to DBD structures of the OmpR/PhoB subfamily of bacterial RRs. To identify ArsR protein elements that potentially bind target DNA sequences and thereby regulate gene transcription in H. pylori, we modeled ArsR-DBD in complex with a putative DNA target. Additionally, we identified novel members of the ArsRS regulon by analyzing ArsR binding to the promoter sequences of putative target genes. These results broaden our understanding of the ArsRS TCS and its role in regulating gene expression in H. pylori.