CLONING OF AN AVILAMYCIN BIOSYNTHETIC GENE-CLUSTER FROM STREPTOMYCES VIRIDOCHROMOGENES TU57

A 65-kb region of DNA from Streptomyces viridochromogenes Tu57, contai ning genes encoding proteins involved in the biosynthesis of avilamyci ns, was isolated. The DNA sequence of a 6.4-kb fragment from this regi on revealed four open reading frames (ORF1 to ORF4), three of which ar e fully contained within the sequenced fragment, The deduced amino aci d sequence of AviM, encoded by ORF2, shows 37% identity to a 6-methyls alicylic acid synthase from Penicillium patulum, Cultures of S. livida ns TK24 and S. coelicolor CH999 containing plasmids with ORF2 on a 5,5 -kb PstI fragment were able to produce orsellinic acid, an unreduced v ersion of 6-methylsalicylic acid, The amino acid sequence encoded by O RF3 (AviD) is 62% identical to that of StrD, a dTDP-glucose synthase f rom S. griseus, The deduced amino acid sequence of AviE, encoded by OR F4, shows 55% identity to a dTDP-glucose dehydratase (StrE) from S, gr iseus, Gene insertional inactivation experiments of aviE abolished avi lamycin production, indicating the involvement of aviE in the biosynth esis of avilamycins.