The 2.2-Å Structure of the HP0958 Protein from Helicobacter pylori Reveals a Kinked Anti-Parallel Coiled-Coil Hairpin Domain and a Highly Conserved Zn-Ribbon Domain

We have determined the 2.2-Å structure of the HP0958 protein from the human gastric pathogen Helicobacter pylori. HP0958 is essential for flagellum formation and motility. It functions as a chaperone for RpoN (σ54) and also controls the stability and translation of mRNA for the major flagellin subunit FlaA. The protein is composed of a highly elongated and kinked coiled-coil hairpin domain (residues 1–170), followed by a C4 Zn-ribbon domain (residues 174–238). The Zn-ribbon domain is rich in aromatic and positively charged amino acid residues. Electrophoretic mobility shift assays identified residues in a positively charged region of the Zn-ribbon domain of HP0958 whose mutation alters the mobility of an HP0958–flaA mRNA complex. Mutation of surface residues in the coiled-coil domain did not result in an observable change in the mobility of the HP0958–flaA transcript complex. The data thus suggest the arrangement of HP0958 into distinct structural and functional domains.