Exploration of two epimerase homologs in Streptomyces peucetius ATCC 27952
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Streptomyces peucetius ATCC 27952 is a potent producer of the therapeutically important antitumor drug, doxorubicin. S. peucetius contains two deoxythymidine diphospho (dTDP)-4-keto-6-deoxyglucose 3,5-epimerase-encoding genes, dnmU and rmbC, in its genome. While dnmU from the doxorubicin biosynthesis gene cluster is involved in the biosynthesis of dTDP-l-daunosamine, rmbC is involved in the biosynthesis of dTDP-l-rhamnose, a precursor of cell wall biosynthesis. The proteins encoded by dnmU and rmbC share 47 % identity and 64 % similarity with each other. Both enzymes converted the same substrate, dTDP-4-keto-6-deoxy-d-glucose, into dTDP-4-keto-l-rhamnose in vitro. However, when disruption of dnmU or rmbC was carried out, neither gene in S. peucetius compensated for each other’s loss of function in vivo. These results demonstrated that although dnmU and rmbC encode for similar functional proteins, their native roles in their respective biosynthetic pathways in vivo are specific and independent of one other. Moreover, the disruption of rmbC resulted in fragmented mycelia that quickly converted into gray pigmented spores. Additionally, the production of doxorubicin, a major product of S. peucetius, appeared to be abolished after the disruption of rmbC, demonstrating its pleiotropic effect. This adverse effect might have switched on the genes encoding for spore formation, arresting the expression of many genes and, thereby, preventing the production of other metabolites.
KeywordsStreptomyces peucetius dTDP-4-keto-6-deoxyglucose 3,5-epimerase gene Sporulation Doxorubicin
This work was supported by a grant from the Next-Generation BioGreen 21 Program (SSAC, grant no. PJ008013), Rural Development Administration, and the Converging Research Center Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education, Science and Technology (20090082333), Republic of Korea.
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