Cloning and characterization of a glycosyltransferase gene involved in the biosynthesis of anthracycline antibiotic beta-rhodomycin from Streptomyces violaceus.

A glycosyltransferase gene, rhoG, involved in the biosynthesis of the anthracycline antibiotic beta-rhodomycin was isolated as a 4.1-kb DNA fragment containing rhoG and its flanking region from Streptomyces violaceus by degenerate and inverse PCR. Sequencing analysis showed that rhoG was located in a gene cluster involved in the biosynthesis of the constitutive deoxysugar of beta-rhodomycin. The function of rhoG was verified by gene disruption, which was generated by replacing the internal 0.9-kb region of S. violaceus chromosome with a fragment including the SacI-blunted region. The rhoG disruption resulted in complete loss of beta-rhodomycin productivity, along with the accumulation of a non-glycosyl intermediate epsilon-rhodomycinone. In addition, the complementation test demonstrated that rhoG restored beta-rhodomycin production in this gene disruptant. These results indicated that rhoG is the glycosyltransferase gene responsible for the glycosylation of epsilon-rhodomycinone in beta-rhodomycin biosynthesis.