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Efficiency of purine utilization by Helicobacter pylori: roles for adenosine deaminase and a NupC homolog.

Miller EF, Vaish S, Maier RJ - PLoS ONE (2012)

Bottom Line: Helicobacter pylori colonizes the gastric epithelium of humans, yet its specific purine requirements are poorly understood, and the transport mechanisms underlying purine uptake remain unknown.Doubling times in this medium varied between 7 and 14 hours depending on the purine source, with hypoxanthine, inosine and adenosine representing the purines utilized most efficiently for growth.Deletion of the GMP biosynthesis gene guaA had no discernible effect on mouse stomach colonization, in contrast to findings in numerous bacterial pathogens.

View Article: PubMed Central - PubMed

Affiliation: Microbiology Department, The University of Georgia, Athens, Georgia, United States of America.

ABSTRACT
The ability to synthesize and salvage purines is crucial for colonization by a variety of human bacterial pathogens. Helicobacter pylori colonizes the gastric epithelium of humans, yet its specific purine requirements are poorly understood, and the transport mechanisms underlying purine uptake remain unknown. Using a fully defined synthetic growth medium, we determined that H. pylori 26695 possesses a complete salvage pathway that allows for growth on any biological purine nucleobase or nucleoside with the exception of xanthosine. Doubling times in this medium varied between 7 and 14 hours depending on the purine source, with hypoxanthine, inosine and adenosine representing the purines utilized most efficiently for growth. The ability to grow on adenine or adenosine was studied using enzyme assays, revealing deamination of adenosine but not adenine by H. pylori 26695 cell lysates. Using mutant analysis we show that a strain lacking the gene encoding a NupC homolog (HP1180) was growth-retarded in a defined medium supplemented with certain purines. This strain was attenuated for uptake of radiolabeled adenosine, guanosine, and inosine, showing a role for this transporter in uptake of purine nucleosides. Deletion of the GMP biosynthesis gene guaA had no discernible effect on mouse stomach colonization, in contrast to findings in numerous bacterial pathogens. In this study we define a more comprehensive model for purine acquisition and salvage in H. pylori that includes purine uptake by a NupC homolog and catabolism of adenosine via adenosine deaminase.

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Overview of the current model for purine conversions in H. pylori.This network allows for salvage of purine nucleobases and nucleosides, as well as inter-conversion between GMP and AMP. Color code: blue; enzymes that have been studied in H. pylori by mutant analysis and/or biochemistry, green; enzymes for which genes have been identified, but whose role has not yet been confirmed, red; putative functional roles whose genetic basis has not yet been identified. Abbreviations: GuaB, IMP dehydrogenase; GuaA, GMP synthetase; GuaC, GMP reductase; PurA, adenylosuccinate synthetase; PurB, adenylosuccinate lyase; Gpt, hypoxanthine-guanine phosphoribosyl-transferase; Apt, adenine phosphoribosyltransferase; DeoD, purine nucleoside phosphorylase; PunB, purine nucleoside phosphorylase; Ade, adenine deaminase; Add, adenosine deaminase; IMP, inosine monophosphate; XMP, xanthosine monophosphate; GMP, guanosine monophosphate; AMP, adenosine monophosphate.
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pone-0038727-g001: Overview of the current model for purine conversions in H. pylori.This network allows for salvage of purine nucleobases and nucleosides, as well as inter-conversion between GMP and AMP. Color code: blue; enzymes that have been studied in H. pylori by mutant analysis and/or biochemistry, green; enzymes for which genes have been identified, but whose role has not yet been confirmed, red; putative functional roles whose genetic basis has not yet been identified. Abbreviations: GuaB, IMP dehydrogenase; GuaA, GMP synthetase; GuaC, GMP reductase; PurA, adenylosuccinate synthetase; PurB, adenylosuccinate lyase; Gpt, hypoxanthine-guanine phosphoribosyl-transferase; Apt, adenine phosphoribosyltransferase; DeoD, purine nucleoside phosphorylase; PunB, purine nucleoside phosphorylase; Ade, adenine deaminase; Add, adenosine deaminase; IMP, inosine monophosphate; XMP, xanthosine monophosphate; GMP, guanosine monophosphate; AMP, adenosine monophosphate.

Mentions: It was recently shown that, in contrast to previous reports, purines are absolutely required for growth of H. pylori 26695 (Abstract no. 2273, Miller, E. F. & Maier, R. J., Annual Meeting of the American Society for Microbiology, May 2011), a result confirmed for three other strains of H. pylori[5]. These observations corroborate predictions made from the RAST-annotated H. pylori genomes, which all lack the pathway for de novo IMP synthesis [6]. H. pylori therefore relies on a purine salvage pathway (Figure 1), which has been partially characterized already [5], [7], [8]. Although several different strains were used for these prior studies, the gene homologs for purine salvage are well-conserved among the sequenced strains of H. pylori, making it likely that purine utilization is similar across strains [6].


Efficiency of purine utilization by Helicobacter pylori: roles for adenosine deaminase and a NupC homolog.

Miller EF, Vaish S, Maier RJ - PLoS ONE (2012)

Overview of the current model for purine conversions in H. pylori.This network allows for salvage of purine nucleobases and nucleosides, as well as inter-conversion between GMP and AMP. Color code: blue; enzymes that have been studied in H. pylori by mutant analysis and/or biochemistry, green; enzymes for which genes have been identified, but whose role has not yet been confirmed, red; putative functional roles whose genetic basis has not yet been identified. Abbreviations: GuaB, IMP dehydrogenase; GuaA, GMP synthetase; GuaC, GMP reductase; PurA, adenylosuccinate synthetase; PurB, adenylosuccinate lyase; Gpt, hypoxanthine-guanine phosphoribosyl-transferase; Apt, adenine phosphoribosyltransferase; DeoD, purine nucleoside phosphorylase; PunB, purine nucleoside phosphorylase; Ade, adenine deaminase; Add, adenosine deaminase; IMP, inosine monophosphate; XMP, xanthosine monophosphate; GMP, guanosine monophosphate; AMP, adenosine monophosphate.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3368855&req=5

pone-0038727-g001: Overview of the current model for purine conversions in H. pylori.This network allows for salvage of purine nucleobases and nucleosides, as well as inter-conversion between GMP and AMP. Color code: blue; enzymes that have been studied in H. pylori by mutant analysis and/or biochemistry, green; enzymes for which genes have been identified, but whose role has not yet been confirmed, red; putative functional roles whose genetic basis has not yet been identified. Abbreviations: GuaB, IMP dehydrogenase; GuaA, GMP synthetase; GuaC, GMP reductase; PurA, adenylosuccinate synthetase; PurB, adenylosuccinate lyase; Gpt, hypoxanthine-guanine phosphoribosyl-transferase; Apt, adenine phosphoribosyltransferase; DeoD, purine nucleoside phosphorylase; PunB, purine nucleoside phosphorylase; Ade, adenine deaminase; Add, adenosine deaminase; IMP, inosine monophosphate; XMP, xanthosine monophosphate; GMP, guanosine monophosphate; AMP, adenosine monophosphate.
Mentions: It was recently shown that, in contrast to previous reports, purines are absolutely required for growth of H. pylori 26695 (Abstract no. 2273, Miller, E. F. & Maier, R. J., Annual Meeting of the American Society for Microbiology, May 2011), a result confirmed for three other strains of H. pylori[5]. These observations corroborate predictions made from the RAST-annotated H. pylori genomes, which all lack the pathway for de novo IMP synthesis [6]. H. pylori therefore relies on a purine salvage pathway (Figure 1), which has been partially characterized already [5], [7], [8]. Although several different strains were used for these prior studies, the gene homologs for purine salvage are well-conserved among the sequenced strains of H. pylori, making it likely that purine utilization is similar across strains [6].

Bottom Line: Helicobacter pylori colonizes the gastric epithelium of humans, yet its specific purine requirements are poorly understood, and the transport mechanisms underlying purine uptake remain unknown.Doubling times in this medium varied between 7 and 14 hours depending on the purine source, with hypoxanthine, inosine and adenosine representing the purines utilized most efficiently for growth.Deletion of the GMP biosynthesis gene guaA had no discernible effect on mouse stomach colonization, in contrast to findings in numerous bacterial pathogens.

View Article: PubMed Central - PubMed

Affiliation: Microbiology Department, The University of Georgia, Athens, Georgia, United States of America.

ABSTRACT
The ability to synthesize and salvage purines is crucial for colonization by a variety of human bacterial pathogens. Helicobacter pylori colonizes the gastric epithelium of humans, yet its specific purine requirements are poorly understood, and the transport mechanisms underlying purine uptake remain unknown. Using a fully defined synthetic growth medium, we determined that H. pylori 26695 possesses a complete salvage pathway that allows for growth on any biological purine nucleobase or nucleoside with the exception of xanthosine. Doubling times in this medium varied between 7 and 14 hours depending on the purine source, with hypoxanthine, inosine and adenosine representing the purines utilized most efficiently for growth. The ability to grow on adenine or adenosine was studied using enzyme assays, revealing deamination of adenosine but not adenine by H. pylori 26695 cell lysates. Using mutant analysis we show that a strain lacking the gene encoding a NupC homolog (HP1180) was growth-retarded in a defined medium supplemented with certain purines. This strain was attenuated for uptake of radiolabeled adenosine, guanosine, and inosine, showing a role for this transporter in uptake of purine nucleosides. Deletion of the GMP biosynthesis gene guaA had no discernible effect on mouse stomach colonization, in contrast to findings in numerous bacterial pathogens. In this study we define a more comprehensive model for purine acquisition and salvage in H. pylori that includes purine uptake by a NupC homolog and catabolism of adenosine via adenosine deaminase.

Show MeSH
Related in: MedlinePlus