A Critical Role for the Putative NCS2 Nucleobase Permease YjcD in the Sensitivity of <named-content content-type="genus-species">Escherichia coli</named-content> to Cytotoxic and Mutagenic Purine Analogs
ABSTRACT The base analogs 6-N-hydroxylaminopurine (HAP) and 2-amino-HAP (AHAP) are potent mutagens in bacteria and eukaryotic organisms. Previously, we demonstrated that a defect in the Escherichia coli ycbX gene, encoding a molybdenum cofactor-dependent oxidoreductase, dramatically enhances sensiti...
| Main Authors: | , , , |
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| Format: | Article |
| Language: | English |
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American Society for Microbiology
2013-12-01
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| Series: | mBio |
| Online Access: | https://journals.asm.org/doi/10.1128/mBio.00661-13 |
| _version_ | 1819203027880378368 |
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| author | Stanislav G. Kozmin Elena I. Stepchenkova Stephen C. Chow Roel M. Schaaper |
| author_facet | Stanislav G. Kozmin Elena I. Stepchenkova Stephen C. Chow Roel M. Schaaper |
| author_sort | Stanislav G. Kozmin |
| collection | DOAJ |
| description | ABSTRACT The base analogs 6-N-hydroxylaminopurine (HAP) and 2-amino-HAP (AHAP) are potent mutagens in bacteria and eukaryotic organisms. Previously, we demonstrated that a defect in the Escherichia coli ycbX gene, encoding a molybdenum cofactor-dependent oxidoreductase, dramatically enhances sensitivity to the toxic and mutagenic action of these agents. In the present study, we describe the discovery and properties of a novel suppressor locus, yjcD, that strongly reduces the HAP sensitivity of the ycbX strain. Suppressor effects are also observed for other purine analogs, like AHAP, 6-mercaptopurine, 6-thioguanine, and 2-aminopurine. In contrast, the yjcD defect did not affect the sensitivity to the pyrimidine analog 5-fluorouracil. Homology searches have predicted that yjcD encodes a putative permease of the NCS2 family of nucleobase transporters. We further investigated the effects of inactivation of all other members of the NCS2 family, XanQ, XanP, PurP, UacT, UraA, RutG, YgfQ, YicO, and YbbY, and of the NCS1 family nucleobase permeases CodB and YbbW. None of these other defects significantly affected sensitivity to either HAP or AHAP. The combined data strongly suggest that YjcD is the primary importer for modified purine bases. We also present data showing that this protein may, in fact, also be a principal permease involved in transport of the normal purines guanine, hypoxanthine, and/or xanthine. IMPORTANCE Nucleotide metabolism is a critical aspect of the overall metabolism of the cell, as it is central to the core processes of RNA and DNA synthesis. At the same time, nucleotide metabolism can be subverted by analogs of the normal DNA or RNA bases, leading to highly toxic and mutagenic effects. Thus, understanding how cells process both normal and modified bases is of fundamental importance. This work describes a novel suppressor of the toxicity of certain modified purine bases in the bacterium Escherichia coli. This suppressor encodes a putative high-affinity nucleobase transporter that mediates the import of the modified purine bases. It is also a likely candidate for the long-sought high-affinity importer for the normal purines, like guanine and hypoxanthine. |
| first_indexed | 2024-12-23T04:13:24Z |
| format | Article |
| id | doaj.art-68a2d8d2cfe84970ba00000775f93822 |
| institution | Directory Open Access Journal |
| issn | 2150-7511 |
| language | English |
| last_indexed | 2024-12-23T04:13:24Z |
| publishDate | 2013-12-01 |
| publisher | American Society for Microbiology |
| record_format | Article |
| series | mBio |
| spelling | doaj.art-68a2d8d2cfe84970ba00000775f938222022-12-21T18:00:25ZengAmerican Society for MicrobiologymBio2150-75112013-12-014610.1128/mBio.00661-13A Critical Role for the Putative NCS2 Nucleobase Permease YjcD in the Sensitivity of <named-content content-type="genus-species">Escherichia coli</named-content> to Cytotoxic and Mutagenic Purine AnalogsStanislav G. Kozmin0Elena I. Stepchenkova1Stephen C. Chow2Roel M. Schaaper3Laboratory of Molecular Genetics, National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina, USALaboratory of Molecular Genetics, National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina, USALaboratory of Molecular Genetics, National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina, USALaboratory of Molecular Genetics, National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina, USAABSTRACT The base analogs 6-N-hydroxylaminopurine (HAP) and 2-amino-HAP (AHAP) are potent mutagens in bacteria and eukaryotic organisms. Previously, we demonstrated that a defect in the Escherichia coli ycbX gene, encoding a molybdenum cofactor-dependent oxidoreductase, dramatically enhances sensitivity to the toxic and mutagenic action of these agents. In the present study, we describe the discovery and properties of a novel suppressor locus, yjcD, that strongly reduces the HAP sensitivity of the ycbX strain. Suppressor effects are also observed for other purine analogs, like AHAP, 6-mercaptopurine, 6-thioguanine, and 2-aminopurine. In contrast, the yjcD defect did not affect the sensitivity to the pyrimidine analog 5-fluorouracil. Homology searches have predicted that yjcD encodes a putative permease of the NCS2 family of nucleobase transporters. We further investigated the effects of inactivation of all other members of the NCS2 family, XanQ, XanP, PurP, UacT, UraA, RutG, YgfQ, YicO, and YbbY, and of the NCS1 family nucleobase permeases CodB and YbbW. None of these other defects significantly affected sensitivity to either HAP or AHAP. The combined data strongly suggest that YjcD is the primary importer for modified purine bases. We also present data showing that this protein may, in fact, also be a principal permease involved in transport of the normal purines guanine, hypoxanthine, and/or xanthine. IMPORTANCE Nucleotide metabolism is a critical aspect of the overall metabolism of the cell, as it is central to the core processes of RNA and DNA synthesis. At the same time, nucleotide metabolism can be subverted by analogs of the normal DNA or RNA bases, leading to highly toxic and mutagenic effects. Thus, understanding how cells process both normal and modified bases is of fundamental importance. This work describes a novel suppressor of the toxicity of certain modified purine bases in the bacterium Escherichia coli. This suppressor encodes a putative high-affinity nucleobase transporter that mediates the import of the modified purine bases. It is also a likely candidate for the long-sought high-affinity importer for the normal purines, like guanine and hypoxanthine.https://journals.asm.org/doi/10.1128/mBio.00661-13 |
| spellingShingle | Stanislav G. Kozmin Elena I. Stepchenkova Stephen C. Chow Roel M. Schaaper A Critical Role for the Putative NCS2 Nucleobase Permease YjcD in the Sensitivity of <named-content content-type="genus-species">Escherichia coli</named-content> to Cytotoxic and Mutagenic Purine Analogs mBio |
| title | A Critical Role for the Putative NCS2 Nucleobase Permease YjcD in the Sensitivity of <named-content content-type="genus-species">Escherichia coli</named-content> to Cytotoxic and Mutagenic Purine Analogs |
| title_full | A Critical Role for the Putative NCS2 Nucleobase Permease YjcD in the Sensitivity of <named-content content-type="genus-species">Escherichia coli</named-content> to Cytotoxic and Mutagenic Purine Analogs |
| title_fullStr | A Critical Role for the Putative NCS2 Nucleobase Permease YjcD in the Sensitivity of <named-content content-type="genus-species">Escherichia coli</named-content> to Cytotoxic and Mutagenic Purine Analogs |
| title_full_unstemmed | A Critical Role for the Putative NCS2 Nucleobase Permease YjcD in the Sensitivity of <named-content content-type="genus-species">Escherichia coli</named-content> to Cytotoxic and Mutagenic Purine Analogs |
| title_short | A Critical Role for the Putative NCS2 Nucleobase Permease YjcD in the Sensitivity of <named-content content-type="genus-species">Escherichia coli</named-content> to Cytotoxic and Mutagenic Purine Analogs |
| title_sort | critical role for the putative ncs2 nucleobase permease yjcd in the sensitivity of named content content type genus species escherichia coli named content to cytotoxic and mutagenic purine analogs |
| url | https://journals.asm.org/doi/10.1128/mBio.00661-13 |
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