Cloning and Characterization of a Gene Cluster for Hatomarubigin Biosynthesis in Streptomyces sp. Strain 2238-SVT4

Streptomyces sp. strain 2238-SVT4 produces hatomarubigins A, B, C, and D, which belong to the angucycline family. Among them, hatomarubigin D has a unique dimeric structure with a methylene linkage. PCR using aromatase and cyclase gene-specific primers identified the hrb gene cluster for angucycline biosynthesis in Streptomyces sp. 2238-SVT4. The cluster consisted of 30 open reading frames, including those for the minimal polyketide synthase, ketoreductase, aromatase, cyclase, O-methyltransferase, oxidoreductase, and oxygenase genes. Expression of a part of the gene cluster containing hrbR1 to hrbX in Streptomyces lividans TK23 resulted in the production of hatomarubigins A, B, and C. Hatomarubigin D was obtained from the conversion of hatomarubigin C by a purified enzyme encoded by hrbY, among the remaining genes.The angucycline antibiotics are a large group of naturally occurring aromatic polyketides of microbial origin (11, 15). They exhibit a wide range of biological activities, which include antibacterial, antiviral, antitumor, enzyme inhibitory, and platelet aggregation inhibitory effects. Although all the members contain a benz[a]anthraquinone skeleton of decaketide origin, their structural diversity is very broad and they have a wide variety of oxidation states. Hatomarubigins A, B, C, and D (Fig. ​(Fig.1)1) belong to the angucycline family and reverse colchicine resistance in multidrug-resistant tumor cells (8). Among them, hatomarubigin D is a unique hatomarubigin C dimer with a methylene linkage. Such a dimer has not been reported previously, and little is known about the mechanism of the methylene bridge formation between two aromatic rings. In this study, a gene cluster for hatomarubigin biosynthesis was identified in Streptomyces sp. strain 2238-SVT4, and a part of the gene cluster was expressed in Streptomyces lividans to produce the hatomarubigins.Open in a separate windowFIG. 1.Structures of angucycline antibiotics.