In Salmonella, several flagellar chaperones have been identified. FlgN has chaperone activity for the hook proteins FlgL and FlgK. The chaperone FliT is dedicated to the capping protein FliD, and FliS to the flagellin
FliC [16–18]. The ablation of genes encoding FlgN, FliT and FliS impairs the stability and the secretion of their dedicated substrates FlgK, FlgL, FliC this website and FliD [16, 19]. Flagellar biogenesis has been extensively investigated in Salmonella and E. coli [15, 20, 21]. Annotation of two H. pylori genomes identified homologues of most flagellar genes of the Salmonella/E. coli paradigm [22–25]. However, some flagellar homologues have not been found in H. pylori, presumably due to low sequence identity. Previous bioinformatics searches, targeting only functional domains, were successfully performed to identify the anti-sigma factor FlgM [13, 14], and FliK was also identified by a bioinformatic approach . In an effort to identify novel flagellar genes in sequenced H. pylori genomes, bioinformatic
analysis focusing on identification of specific and conserved domains of flagellar genes was performed. In Salmonella, FliJ is a 17 kDa protein with a relative abundance of charged residues. Fraser and colleagues showed that FliJ Protein Tyrosine Kinase inhibitor in Salmonella interacts with FliH (the presumptive inhibitor of the FliI ATPase) and FlhA (a flagellar biosynthesis protein) . FliJ was initially thought to display chaperone activity . However, a recent study clearly indicated that FliJ is not a export chaperone for subunits of the hook and the filament . FliJ binds to export chaperones FlgN and FliT and is involved in an escort mechanism, whereby FliJ promotes cycling of the export chaperones FlgN and FliT. A FliJ homologue was not found in the initial annotation of two H. pylori genomes, nor incidentally were homologues for FlgN or FliT [22, 23, 25]. Although searches based on the full-length sequence of FliJ did not identify any H. pylori homologues, a search using only the essential FliJ domain (N-terminal coiled-coil domain) did reveal a potential homologue (P. W. O’Toole, unpublished).
This analysis identified HP0256, encoding a hypothetical protein Urease with unknown function and a predicted coiled coil domain. In the present study, we phenotypically characterized a mutant lacking the HP0256 gene product and investigated the function of HP0256 in the flagellar regulon using global transcript analysis. The data suggest a novel role for HP0256 in motility but not flagellum assembly, and involvement in production of cell surface proteins. Results Bioinformatic analysis of HP0256 PSI-BLAST searches using the full length FliJ sequence from Salmonella did not identify any homologues in H. pylori. However, using only the FliJ N-terminal coiled-coil domain as a search query, HP0256 was identified as a potential FliJ homologue. The annotation of this H.