Probing of bismuth antiulcer drug targets in H. pylori by laser ablation-inductively coupled plasma mass spectrometry

A method that allows partial denaturation of protein ligands in Bi- and Zn-protein complexes, leaving the metal coordination centre intact, was developed. It was based on the reduction of the S-S bridges with tris(2-carboxyl)phosphine followed by derivatization with iodoacetamide. Consequently conditions that allow the separation of Bi- and Zn-protein complexes using SDS electrophoresis were found. The separation efficiency was much higher than that in non-denaturating blue native electrophoresis. The method allowed the detection of seven Bi-binding protein candidates in H. pylori treated with bismuth subcitrate, some of which-fructose-bisphosphate aldolase (33.6 kDa), urease alpha subunit (26.4 kDa), and the 16.8 kDa proteins: 30S ribosomal protein S6 and neutrophil activating protein (NapA)-were bio-induced during the treatment. The method also allowed the monitoring of the changes in the Zn-proteome during treatment of H. pylori with the Bi-drug, which was found to increase the concentration of the Zn-binding proteins with particularly strong expression of the urease, S-adenosylmethionine synthetase and the above 16.8 kDa proteins.