Comparative analysis of the Hom family of outer membrane proteins in isolates from two geographically distinct regions: The United States and South Korea

Background: Helicobacter pylori encodes numerous outer membrane proteins (OMPs), but only a few have been characterized in depth. Deletion, duplication, and allelic variation of many of the H. pylori OMPs have been reported, which suggests that these proteins may play key roles in host adaptation. Herein, we characterize the variation observed within the Hom family of OMPs in H. pylori obtained from two geographically distinct populations. Materials and Methods: PCR genotyping of the hom genes was carried out using clinical isolates from South Korea and the United States. A combination of statistical, phylogenetic, and protein modeling analyses was conducted to further characterize the hom variants. Results: Variations in the closely related hom genes, homA and homB, occur in regions that are predicted to encode environmentally exposed loops. A similar phenomenon is true for homC^S as compared to homC^L. Conversely, little variation was observed in homD. Certain variants of the Hom family of proteins were more prominent in isolates from the Korean population as compared to isolates from the United States. Conclusion: En masse, our data show that the homA, homB, and homC profiles vary based upon the geographic origin of the strain; however, the fourth member of the hom family, homD, is more highly conserved. Additionally, protein topology modeling showed that many of the less well-conserved regions between homA and homB and between homC^S and homC^L corresponded to predicted environmentally exposed loops, suggesting that the divergence of the Hom family may be due to host adaptation/pressure.