Towards a new therapeutic target: Helicobacter pylori flavodoxin

Abstract

Helicobacter pylori flavodoxin is the electronic acceptor of the pyruvate–oxidoreductase complex (POR) that catalyzes pyruvate oxidative decarboxilation. Inactivation of this metabolic route precludes bacterial survival. Because flavodoxin is not present in the human host, substances interfering electronic transport from POR might be well suited for eradication therapies against the bacterium. H. pylori flavodoxin presents a peculiar cofactor (FMN) binding site, compared to other known flavodoxins, where a conserved aromatic residue is replaced by alanine. A cavity thus appears under the cofactor that can be filled with small organic molecules. We have cloned H. pylori fldA gene, expressed the protein in Escherichia coli and characterized the purified flavodoxin. Thermal up-shift assays of flavodoxin with different concentrations of benzylamine, as well as fluorescence titration experiments indicate benzylamine binds in the pocket near the FMN binding site. It seems thus that low affinity inhibitors of H. pylori flavodoxin can be easily found that, after improvement, may give rise to leads.