Concerted evolution between duplicated genetic elements in Helicobacter pylori

David T. Pride, Martin J. Blaser

Research output: Contribution to journalArticlepeer-review

71 Scopus citations

Abstract

The Helicobacter pylori genome includes a family of outer membrane proteins (OMPs) with substantial N and C-terminal identity. To better understand their evolution, the nucleotide sequences for two members, babA and babB, were determined from a worldwide group of 23 strains. The geographic origin of each strain was found to be the major determinant of phylogenetic structure, with strains of Eastern and Western origin showing greatest divergence. For strains 96-10 (Japan) and 96-74 (USA), the 5′ regions of babB are replaced with babA sequences, demonstrating that recombination occurs between the two loci. babA and babB have nearly equivalent variation in nucleotide and amino acid identity, and frequencies of synonymous and non-synonymous substitutions. Both genes have segmental conservation but within the 3′ segment, substitution patterns are nearly identical. Although babA and babB 5′ and mid-region segment phylogenies show strong interstrain similarity, the 3′ segments show strong intrastrain similarity, indicative of concerted evolution. Within these 3′ segments, the lower intrastrain than interstrain frequencies of nucleotide substitutions, which are below mean background H. pylori substitution frequencies, indicate selection against intrastrain diversification. Since babA/babB gene conversions likely underlie the concerted evolution of the 3′ segments, in an experimental system, we demonstrate that gene conversions can frequently (10-3) occur in H. pylori. That these events are recA-dependent and DNase-resistant indicates their likely cause is intragenomic recombination.

Original languageEnglish (US)
Pages (from-to)629-642
Number of pages14
JournalJournal of molecular biology
Volume316
Issue number3
DOIs
StatePublished - Jan 1 2002
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Structural Biology
  • Molecular Biology

Keywords

  • Concerted evolution
  • Gene conversion
  • Helicobacter pylori
  • babA
  • babB

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