Functional analysis of hatomarubigin biosynthesis genes and production of a new hatomarubigin using a heterologous expression system

The function of hatomarubigin biosynthesis genes was analyzed by heterologous expression of the hrb gene cluster. Streptomyces lividans carrying a gene cluster consisting of 25 genes (hrbR1-hrbX) with hrbY was found to produce all the known hatomarubigins including hatomarubigin D, which has a unique dimeric angucycline with a methylene linkage. Gene disruption was used in this heterologous expression system to analyze the function of hrbF, a gene with no homology to any known angucycline biosynthesis genes. A new metabolite was detected in the fermented broth of S. lividans expressing the hrb genes lacking hrbF and was designated hatomarubigin F. This compound was identified as 5-hydroxyhatomarubigin E by NMR spectroscopic analysis, suggesting that HrbF regulates the regiospecificity of oxygenation enzymes.