Proteomic analysis of a ferric uptake regulator mutant of Helicobacter pylori: regulation of Helicobacter pylori gene expression by ferric uptake regulator and iron.

The ferric uptake regulator (Fur) protein is a Fe(2+)-dependent transcriptional repressor that binds to the Fur-box of bacterial promoters and down-regulates gene expression. In this study, to investigate global gene regulation by Fur in response to iron in Helicobacter pylori, a causative agent of human gastric diseases, we compared the proteome profiles of the H. pylori strain 26695 and its isogenic fur mutant grown under iron-rich and iron-depleted conditions. In total, 93 protein spots were found to be up- or down-regulated by more than 2-fold by either a fur mutation or iron-depletion. From these, 39 spots were identified by matrix-assisted laser desorption/ionization time of flight analysis to be 29 different proteins of diverse functions, including energy metabolism, transcription and translation, detoxification, biosynthesis of amino acids and nucleotides and production of the cell envelope. Expression of six proteins was found to be higher in the fur mutant than in the wild-type bacteria, indicating Fur-mediated repression. Eleven proteins were activated by Fur; five responded to iron and the others were not iron-responsive. The remaining 12 proteins were not under Fur-regulation but responded to iron in a positive or negative manner. Seven different types of gene regulation via Fur and iron were identified. These findings demonstrate that the H. pylori Fur protein functions as a classical transcriptional repressor but can also function as an activator, providing evidence for the presence of Fur-mediated positive regulation in H. pylori.