NONMOTILE MUTANTS OF HELICOBACTER-PYLORI AND HELICOBACTER-MUSTELAE DEFECTIVE IN FLAGELLAR HOOK PRODUCTION

Flagellar hooks were purified from Helicobacter pylori and Helicobacte r mustelae. The 70 x 16 nm H. pylori hook was composed of FlgE subunit s of 78 kDa, while the 72 x 16 nm H. mustelae hook was composed of 87 kDa subunits. N-terminal sequence was obtained for the FlgE proteins o f both species, and for an internal H. mustelae FlgE peptide. Degenera te oligonucleotide primers allowed amplification of a 1.2 kb fragment from the H. mustelae chromosome, which carried part of the flgE gene. The corresponding H. pylori gene was cloned by immunoscreening of a ge nomic library constructed in lambda ZAP Express. The translated H. pyl ori flgE sequence indicated a protein with limited homology with the h ook proteins from Salmonella typhimurium and Treponema phagedenis. Mut ants of H. pylori and H. mustelae defective in hook production generat ed by allele replacement were nonmotile and devoid of flagellar filame nts but produced both flagellin subunits, which were localized in the soluble fraction of the cell. The level of flagellin production was un changed in the mutants, indicating that the regulation of flagellin ex pression in Helicobacter differs from that in the Enterobacteriaceae.