title: Characterization of two glycosyltransferases involved in early glycosylation steps during biosynthesis of the antitumor polyketide mithramycin by Streptomyces argillaceus.
abstract: A 2,580-bp region of the chromosome of Streptomyces argillaceus, the producer of the antitumor polyketide mithramycin, was sequenced. Analysis of the nucleotide sequence revealed the presence of two genes (mtmGIII and mtmGIV) encoding proteins that showed a high degree of similarity to glycosyltransferases involved in the biosynthesis of various antibiotics and antitumor drugs. Independent insertional inactivation of both genes produced mutants that did not synthesize mithramycin but accumulated several mithramycin intermediates. Both mutants accumulated premithramycinone, a non-glycosylated intermediate in mithramycin biosynthesis. The mutant affected in the mtmGIII gene also accumulated premithramycin A1, which contains premithramycinone as the aglycon unit and a D-olivose attached at C-12a-O. These experiments demonstrate that the glycosyltransferases MtmGIV and MtmGIII catalyze the first two glycosylation steps in mithramycin biosynthesis. A model is proposed for the glycosylation steps in mithramycin biosynthesis.
authors.affiliation: Departamento de Biología Funcional e Instituto Universitario de Oncología del Principado de Asturias, Universidad de Oviedo, Spain.
authors.forename: G
authors.initials: G
authors.lastname: Blanco
authors.forename: E
authors.initials: E
authors.lastname: Fernández
authors.forename: M J
authors.initials: MJ
authors.lastname: Fernández
authors.forename: A F
authors.initials: AF
authors.lastname: Braña
authors.forename: U
authors.initials: U
authors.lastname: Weissbach
authors.forename: E
authors.initials: E
authors.lastname: Künzel
authors.forename: J
authors.initials: J
authors.lastname: Rohr
authors.forename: C
authors.initials: C
authors.lastname: Méndez
authors.forename: J A
authors.initials: JA
authors.lastname: Salas
mesh_terms: D000595:Amino Acid Sequence; D000903:Antibiotics, Antineoplastic / Q000096:biosynthesis* / Q000737:chemistry; D001483:Base Sequence; D004269:DNA, Bacterial / Q000235:genetics; D018390:Gene Targeting; D005798:Genes, Bacterial; D006031:Glycosylation; D016695:Glycosyltransferases / Q000235:genetics / Q000378:metabolism*; D008954:Models, Biological; D008969:Molecular Sequence Data; D016254:Mutagenesis, Insertional; D009154:Mutation; D010802:Phylogeny; D008926:Plicamycin / Q000096:biosynthesis* / Q000737:chemistry; D017386:Sequence Homology, Amino Acid; D013302:Streptomyces / Q000201:enzymology / Q000235:genetics / Q000378:metabolism*
chemical_list: D000903:Antibiotics, Antineoplastic; D004269:DNA, Bacterial; D016695:Glycosyltransferases; D008926:Plicamycin