RESUMEN
C-Glycosylation in the biosynthesis of bioactive natural products is quite unique, which has not been studied well. Medermycin, as an antitumor agent in the family of pyranonaphthoquinone antibiotics, is featured with unique C-glycosylation. Here, a new C-glycosyltransferase (C-GT) Med-8 was identified to be essential for the biosynthesis of medermycin, as the first example of C-GT to recognize a rare deoxyaminosugar (angolosamine). med-8 and six genes (med-14, -15, -16, -17, -18, and -20 located in the medermycin biosynthetic gene cluster) predicted for the biosynthesis of angolosamine were proved to be functional and sufficient for C-glycosylation. A C-glycosylation cassette composed of these seven genes could convert a proposed substrate into a C-glycosylated product. In conclusion, these genes involved in the C-glycosylation of medermycin were functionally identified and biosynthetically engineered, and they provided the possibility of producing new C-glycosylated compounds.
Asunto(s)
Proteínas Bacterianas/metabolismo , Vías Biosintéticas , Glicosiltransferasas/metabolismo , Streptomyces/metabolismo , Proteínas Bacterianas/genética , Genes Bacterianos , Glicosiltransferasas/genética , Modelos Moleculares , Familia de Multigenes , Naftoquinonas/metabolismo , Filogenia , Streptomyces/genéticaAsunto(s)
Proteínas Bacterianas/metabolismo , Vías Biosintéticas/genética , Naftoquinonas/aislamiento & purificación , Naftoquinonas/metabolismo , Streptomyces coelicolor/enzimología , Streptomyces coelicolor/metabolismo , Antraquinonas/metabolismo , Proteínas Bacterianas/genética , Estructura Molecular , Proteínas Mutantes/genética , Proteínas Mutantes/metabolismo , Naftoquinonas/química , Análisis Espectral , Streptomyces coelicolor/genéticaRESUMEN
LanV is involved in the biosynthesis of landomycin A. The exact function of this enzyme was elucidated with combinatorial biosynthesis by using Streptomyces fradiae mutants that produce urdamycin A. After expression of lanV in S. fradiae DeltaurdM, which is a mutant that accumulates rabelomycin, urdamycinon B and urdamycin B were found to be produced by the strain. This result indicates that LanV is involved in the 6-ketoreduction of the angucycline core, which preceeds a 5,6-dehydration reaction. 9-C-D-Olivosyltetrangulol was also produced by this strain; this demonstrates that LanV catalyses the aromatization of ring A of the angucycline structure. Coexpression of lanV and lanGT2 in S. fradiae AO, a mutant that lacks all four urdamycin glycosyltransferases, resulted in the production of tetrangulol and the glycoside landomycin H, both of which have an aromatic ring A. As glycosylated angucyclines were not observed after expression of lanGT2 in the absence of lanV, we conclude that LanGT2 needs an aromatized ring A for substrate recognition.