Characterization of Helicobacter pylori σ54 promoter-binding activity

Abstract

Several Helicobacter pylori flagellar genes require σ54 for their transcription. Predicted H. pyloriσ54-dependent promoters display a preference for A at position -23 instead of C or T as occurs in promoters from most other bacteria. Substitution of the A at position -23 of the H. pylori flaB promoter with a C did not effect expression of a flaB′-′xylE reporter gene in H. pylori, whereas T or G substitutions at this position drastically reduced expression. Results of gel mobility shift assays that used DNA probes corresponding to core promoter sequences and a H. pyloriσ54 protein fused to the Escherichia coli maltose-binding protein suggested that H. pyloriσ54 has a higher affinity for promoters with an A at the -23 position. The failure to observe an effect on expression for the flaB mutant promoter with the A to C substitution at the -23 position indicates that sequences flanking the core promoter region may assist binding of H. pyloriσ54 to the mutant flaB promoter. Alternatively, H. pylori RNA polymerase or the σ54-dependent activator FlgR may compensate for the reduced affinity of σ54 for the mutant flaB promoter. © 2006 Federation of European Microbiological Societies Published by Blackwell Publishing Ltd. All rights reserved.