The C terminus of HspA--a potential target for native Ni(II) and Bi(III) anti-ulcer drugs.

HspA, a protein crucial for nickel homeostasis in Helicobacter pylori (H. pylori), has a unique histidine- and cysteine-rich domain at the C terminus. In this work, we compared the coordination of nickel (the natural co-factor) and bismuth (inhibitor) to this domain (Ac-ACCHDHKKH-NH(2)) and to a reference peptide (Ac-CHCH-NH(2)). Potentiometric, CD, UV-Vis spectroscopic and NMR methods have shown that bismuth binds incomparably stronger than nickel; the same data shows the impact of histidines on such a binding. Our results are in good agreement with earlier biological data and suggest that HspA can be a potential target of the bismuth anti-ulcer drug against H. pylori.