Biosynthesis of anthracyclines: analysis of mutants of Streptomyces sp. strain C5 blocked in daunomycin biosynthesis

Abstract

Streptomyces sp. strain C5, an organism that normally produces baumycins, daunomycin and ε-rhodomycinone, was treaed with N-methyl-N′-nitro-N-nitrosoguanidine (NTG). Mutants blocked at arious points in daunomycin and baumycin production were isolated by screening for altered pigmentation and absnce of bioactivity against Staphylococcus aureus. Examination of the mutants by thin-layer chromatography of their accumulated anthracycline metabolites, by cosynthesis assays, and by extract feeding experiments allowed a classification into six groups. Theses were: dauA, strains that accumulated no anthracyclines but with other blocked mutants cosynthesized anthracyclines (polyketide-synthase-minus mutants); dauG, regulatory mutants that, either alone or mixed with other blocked mutants, accumulated no anthracyclines; dauC, mutants that accumulated aklanonic acid; dauE, mutants that accumulated maggiemycin; dauF, mutants that accumulated aklavinone; and dauH, mutants that accumulated only ε-rhodomycinone. Mutant SC5-24 (dauE), which accumulated that shunt product maggiemycin, was re-mutagenized with NTG to obtain blocked mutants in preceding biosynthetic steps; the three grops of double mutants obtained accumulated aklanonic acid (dauC,E), aklanonic acid methyl ester (dauD,E) and akalviketone (dauE,F).