Negative Involvement of the TetR-type regulator SLCG_2919 in the regulation of lincomycin biosynthesis in Streptomyces lincolnensis .

Lincomycin A (Lin-A) is a widely used anti-bacterial antibiotic fermented by Streptomyces lincolnensis However, the transcriptionally regulatory mechanisms underlying lincomycin biosynthesis have seldom been investigated. Here, we first identified a TetR family transcriptional regulator (TFR), SLCG_2919, negatively modulating lincomycin biosynthesis in S. lincolnensis LCGL. SLCG_2919 was found to specifically bind to promoter regions of the lincomycin biosynthetic gene cluster ( lin cluster), including twenty four structural genes, three resistance genes, and one regulatory gene, and to inhibit the transcription of these genes, demonstrating the directly regulatory role in lincomycin biosynthesis. Further, we found that SLCG_2919 was not auto-regulated, but directly repressed its adjacent gene SLCG_2920 encoding an ATP/GTP binding protein, whose overexpression increased the resistance against lincomycin and Lin-A yields in S.lincolnensis The precise SLCG_2919-binding site within the promoter region of SLCG_2920 was determined by a DNase I footprinting assay and by EMSAs based on base substitution mutagenesis, with the internal 10-nt AT-rich sequence (AAATTATTTA) shown to be essential for SLCG_2919 binding. Our findings indicate that SLCG_2919 is a negative regulator for controlling lincomycin biosynthesis in S. lincolnensis The present study improves our understanding of molecular regulation for lincomycin biosynthesis. IMPORTANCE TetR family transcriptional regulator (TFRs) are generally found to regulate diverse cellular processes in bacteria, especially antibiotic biosynthesis in Streptomyces However, knowledge of their function in lincomycin biosynthesis in S. lincolnensis remains unknown. The present study provides a new insight into the regulation of lincomycin biosynthesis through a TFR, SLCG_2919, that directly modulates lincomycin production and resistance. Intriguingly SLCG_2919 and its adjoining gene SLCG_2920 encoding an ATP/GTP binding protein were extensively distributed in diverse Streptomyces species. In addition, we revealed a new TFR binding motif, in which SLCG_2919 binds to the promoter region of SLCG_2920 , dependent on the intervening AT-rich sequence rather than the flanking inverted repeats found in other TFRs' binding sites. These insights into transcriptional regulation of lincomycin biosynthesis by SLCG_2919 will set a valuable way for genetic engineering of regulatory elements in Streptomyces to improve antibiotic production.