THE STR GENE-CLUSTER FOR THE BIOSYNTHESIS OF 5'-HYDROXYSTREPTOMYCIN IN STREPTOMYCES-GLAUCESCENS GLA.0 (ETH-22794) - NEW OPERONS AND EVIDENCE FOR PATHWAY SPECIFIC REGULATION BY STRR

Two divergently oriented operons, strXU and strVW, located within the gene cluster for 5'-hydroxystreptomycin (5'-OH-Sm) biosynthesis in Str eptomyces glaucescens strain GLA.0 (ETH 22794), were analysed by DNA s equencing and transcription/regulation studies. Three genes, strU and strVW, are conserved in a similar arrangement but in a different locat ion within the str/sts gene cluster of the Sm-producing strain S. gris eus N2-3-11. The four putative products resemble NDP-4-ketohexose 3,5- epimerases (StrX, M(r) 20.2 kDa), NAD(P)-dependent oxidoreductases (St rU, 45.6 kDa), and ABC-transporters (StrV, 61.8 kDa; StrW, 63.4 kDa). These genes are apparently involved in the biosynthesis of 5'-OH-Sm be cause the promoters of both operons are activated in trans by the acti vator StrR of S. griseus N2-3-11, when cloned in S. lividans 66 TK23. A sequence motif resembling the consensus sequence GTTCGActC(N)(11)Cag TcGAAc for binding of StrR was identified within the intergenic region of strX and strV. Specific binding of StrR to this site was demonstra ted by gel retardation assays using purified HisTag-StrR.