Allelic Variation within Helicobacter pylori babA and babB.
Helicobacter pylori strains show both geographic and disease-associated allelic variation. We investigated the diversity present in two genes, babA and babB, which are members of a paralogous family of outer membrane proteins. Eleven family members within a single H. pylori strain, predicted to encode proteins with substantial N- and C-terminal similarity to each other, were classified as babA paralogues. In their central regions, most are less than 54% related to one another. Examining the babA and babB central regions in 42 H. pylori strains from different geographic locales, we identified five different allele groups of babA (AD1 to AD5) and three different allele groups of babB (BD1 to BD3). Phylogenetic analysis revealed that the allelic groupings of babA and babB are independent of one another and that, for both, geographic variation is present. Analysis of synonymous and nonsynonymous substitutions in these regions showed that babA is more diverse, implying an earlier origin than that of the same region of babB, but that the babA diversity region may have more functional constraints. Although recombination has been central to the evolution of both genes, with babA and babB showing low mean compatibility scores and homoplasy ratios of 0.71 and 0.67, respectively, recombination is not sufficient to obscure evidence of clonal descent. Despite the involvement of babA in binding to the host blood group antigen Lewis B, neither the presence of different babA allele groups nor that of different babB allele groups is a determining factor in Lewis B binding of H. pylori strains.
Pride
D T
DT
Division of Infectious Diseases, Department of Medicine, Vanderbilt University School of Medicine and VA Medical Center, Nashville, Tennessee, USA. David.T.Pride@Vanderbilt.edu
Meinersmann
R J
RJ
Blaser
M J
MJ
D018829:Adhesins, Bacterial; D000483:Alleles; D000595:Amino Acid Sequence; D001425:Bacterial Outer Membrane Proteins / Q000235:genetics*; D002352:Carrier Proteins; D014644:Genetic Variation; D016480:Helicobacter pylori / Q000145:classification / Q000235:genetics*; D007983:Lewis Blood Group Antigens / Q000378:metabolism; D008969:Molecular Sequence Data; D010802:Phylogeny; D011995:Recombination, Genetic
D018829:Adhesins, Bacterial; C400429:BabA protein, Helicobacter pylori; D001425:Bacterial Outer Membrane Proteins; D002352:Carrier Proteins; D007983:Lewis Blood Group Antigens