The dgt gene of Escherichia coli facilitates thymine utilization in thymine-requiring strains
Article first published online: 12 JUL 2011
© Published 2011. This article is a US Government work and is in the public domain in the USA
Volume 81, Issue 5, pages 1221–1232, September 2011
How to Cite
Itsko, M. and Schaaper, R. M. (2011), The dgt gene of Escherichia coli facilitates thymine utilization in thymine-requiring strains. Molecular Microbiology, 81: 1221–1232. doi: 10.1111/j.1365-2958.2011.07756.x
- Issue published online: 24 AUG 2011
- Article first published online: 12 JUL 2011
- Accepted manuscript online: 8 JUL 2011 03:06AM EST
- Accepted 14 June, 2011.
The Escherichia coli dGTP triphosphohydrolase (dGTPase) encoded by the dgt gene catalyses the hydrolysis of dGTP to deoxyguanosine and triphosphate. The recent discovery of a mutator effect associated with deletion of dgt indicated participation of the triphosphohydrolase in preventing mutagenesis. Here, we have investigated the possible involvement of dgt in facilitating thymine utilization through its ability to provide intracellular deoxyguanosine, which is readily converted by the DeoD phosphorylase to deoxyribose-1-phosphate, the critical intermediate that enables uptake and utilization of thymine. Indeed, we observed that the minimal amount of thymine required for growth of thymine-requiring (thyA) strains decreased with increased expression level of the dgt gene. As expected, this dgt-mediated effect was dependent on the DeoD purine nucleoside phosphorylase. We also observed that thyA strains experience growth difficulties upon nutritional shift-up and that the dgt gene facilitates adaptation to the new growth conditions. Blockage of the alternative yjjG (dUMP phosphatase) pathway for deoxyribose-1-phosphate generation greatly exacerbated the severity of thymine starvation in enriched media, and under these conditions the dgt pathway becomes crucial in protecting the cells against thymineless death. Overall, our results suggest that the dgt-dependent pathway for deoxyribose-1-phosphate generation may operate under various cell conditions to provide deoxyribosyl donors.