The RecA Protein ofHelicobacter pyloriRequires a Posttranslational Modification for Full Activity

Abstract

The RecA protein is a central component of the homologous recombination machinery and of the SOS system in most bacteria. In performing these functions, it is involved in DNA repair processes and plays an important role in natural transformation competence. This may be especially important in Helicobacter pylori, where an unusually high degree of microdiversity among strains is generated by homologous recombination. We have suggested previously that the H. pylori RecA protein is subject to posttranslational modifications that result in a slight shift in its electrophoretic mobility. Here we show that at least two genes downstream of recA are involved in this modification and that this process is dependent on genes involved in glycosylation and lipopolysaccharide biosynthesis. Site-directed mutagenesis of a putative glycosylation site results in production of an unmodified RecA protein. This posttranslational modification is not involved in membrane targeting or cell division functions but is necessary for the full function of RecA in DNA repair. Thus, it might be an adaptation to the specific requirements of H. pylori in its natural environment.The gram-negative bacterial pathogen Helicobacter pylori is the principal cause of chronic active gastritis and peptic ulcer disease and has been implicated in the development of gastric mucosa-associated lymphoid tissue lymphoma and gastric cancer (29, 40). The very special habitat of H. pylori at the surface of gastric epithelial cells or in the mucus layer covering the epithelium suggests that this bacterium has evolved specialized features for adaptation. A comparison of the two published genome sequences shows a considerable diversity in gene content, with about 7% of all putative genes being strain specific (1). Moreover, some H. pylori strains display high mutation frequencies (3), and more diversity is created by horizontal gene transfer and free recombination between strains (41), although infections with multiple strains are not very common. Since H. pylori is naturally competent for transformation, horizontal gene transfer is supposed to occur mainly by this mechanism.Thus, homologous recombination is an important function which helps to generate diversity, but it is also involved in maintaining genome integrity and thus species barriers (28). These functions are achieved by a complex machinery which is highly regulated and which involves many proteins (9). The RecA protein is one of the central components of this machinery. One of its main functions is the recognition of stretches of single-stranded DNA, which are subsequently complexed by helical RecA filaments. In Escherichia coli, this filamentous form of RecA is activated as a coprotease that regulates cellular functions such as the SOS response or the induction of trans-lesion DNA synthesis. Both this coprotease activity and the recombination function are thought to play major roles in the bacterial response to DNA damage. The RecA protein of H. pylori has likewise been shown to be necessary for DNA repai...

Dual Nuclease and Helicase Activities of Helicobacter pylori AddAB Are Required for DNA Repair, Recombination, and Mouse Infectivity

“…This may reflect the level of expression of the H. pylori genes in E. coli, protein stability, or another factor. One factor that limited RecA protein activity in our experiments may be the reported post-translational modification of H. pylori RecA by glycosylation in H. pylori but not E. coli (73,74). Expression of H. pylori RecA failed to complement the UV sensitivity of an E. coli recA mutant (74).…”

The Sweet Tooth of Bacteria: Common Themes in Bacterial Glycoconjugates

“…was on the glycosylation of RecA in H. pylori. Based on mutational analyses of recA and eno (an enolase homologue), glycosylation was claimed to be required for the full functionality of RecA in response to DNA damage (334). However, glycosylation of RecA needs to be further substantiated, especially in other bacterial species, given its universal role.…”

A Recombination Puzzle Solved: Role for New DNA Repair Systems in Helicobacter pylori Diversity/Persistence

“…Disruption of recA in H. pylori abolished general homologous recombination [65]. Interestingly, H. pylori RecA protein is subject to posttranslational modifications that result in a slight shift in its electrophoretic mobility [67]. One putative mechanism for RecA modification is protein glycosylation.…”

“…H. pylori RecA protein was shown to be membrane associated, but this association is not dependent on the posttranslational modification. The RecA modification is required for full activity of DNA repair [67]. In recent years, the phenotypes of H. pylori recA mutants have been further characterized in comparison with other mutants.…”