Production of 8′-halogenated and 8′-unsubstituted novobiocin derivatives in genetically engineered Streptomyces coelicolor strains

In the present study, we produced a hybrid antibiotic, carrying a chlorine atom instead of a methyl group at position 8 of the aminocoumarin moiety of novobiocin. This compound was not accessible by conventional gene inactivation/gene expression experiments due to difficulties in the genetic manipulation of the novobiocin producer Streptomyces spheroides. However, the desired compound was obtained after modification of the novobiocin biosynthetic gene cluster by using h-Red-mediated recombination in Escherichia coli, followed by integration of the resulting modified cosmid into the PhiC31 attachment site of Streptomyces coelicolor and coexpression of the halogenase Clohal of clorobiocin biosynthesis. The halogenase BhaA, responsible for chlorination of tyrosyl moieties of the glycopeptide antibiotic balhimycin, was unable to functionally replace the halogenase Clo-hal, suggesting that the two enzymes have different substrate specificities.