FIG. 7.

(A) Alignment of the amino acid sequences of the H. pylori (Hp) and E. coli (Ec) NikR proteins with secondary structure elements highlighted and Ni²⁺-binding amino acids shaded as elucidated from the crystal structure of E. coli NikR (24). The N terminus The β-1 strand of the RHH structure responsible for DNA recognition is boxed. (B) Model encompassing the direct interplay of the metal-responsive regulators of H. pylori elucidated in footprinting experiments in the present study (thick lines) and thin lines indicate the interplay reported in previous studies (11, 12, 33) and possibly others. According to gene organization deduced from the genome sequence, the exbB, exbD, and tonB genes appear to constitute an operon.