Conservation, localization and expression of HopZ, a protein involved in adhesion of Helicobacter pylori

From a sarkosyl-insoluble outer membrane fraction prepared from the Helicobacter pylori strain ATCC 43504, 19 proteins could be sequenced N-terminally by Edman degradation. Oligonucleotides were deduced and used for screening of a genomic library. From the isolated genes, five code for different members of a H.pylori outer membrane protein (Hop) family. Among these, the hopZ gene was characterized in more detail. It encodes a protein which was shown to be located at the bacterial surface by immunofluorescence studies. Sequence analysis of the hopZ gene from 15 different H.pylori strains revealed the existence of two alleles and the possible regulation of hopZ expression by slipped-strand mispairing within a CT dinucleotide repeat motif located in the signal-peptide coding region. Among the different strains, the influence of this region on the expression of HopZ was analyzed on a translational level by western blot analysis of bacterial extracts and immunofluorescence studies on intact cells. The protein is expressed only in those strains in which the number of the CT dinucleotide repeats allow for an open reading frame encoding the complete protein. Addionally the function of HopZ was investigated in an adhesion assay. The wild-type strain ATCC 43504 adhered to human gastric epithel cells whereas a knockout mutant strain showed significantly reduced binding to the cells.