Metabolic Engineering of Aminocoumarins: Inactivation of the Methyltransferase Gene cloP and Generation of New Clorobiocin Derivatives in a Heterologous Host

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Abstract
Aminocoumarin antibiotics are highly potent inhibitors of bacterial gyrase and represent a class of antibiotics that are very suitable for the generation of new compounds by metabolic engineering. In this study, the putative methyltransferase gene cloP in the biosynthetic gene cluster of clorobiocin was inactivated. Expression of the modified gene cluster in the heterologous host Streptomyces coelicolor M512 gave three new aminocoumarin antibiotics. The structures of the new compounds were elucidated by MS and 1H NMR, and their antibacterial activities were determined. All three compounds lacked clorobiocin's methyl group at 4-OH of the deoxysugar moiety, noviose. They differed from each other in the position of the 5-methylpyrrole-2-carbonyl group, which was found to be attached to either 2-OH, 3-OH or 4-OH of noviose. Attachment at 4-OH resulted in the highest antibacterial activity. This is the first time that an aminocoumarin antibiotic acylated at 4-OH in noviose has been detected.