AdpA regulates lincomycin and melanin biosynthesis by modulating precursors flux in Streptomyces lincolnensis.

Lincomycin is one of the most important antibiotics. However, transcriptional regulation network of secondary metabolism in Streptomyces lincolnensis, the lincomycin producer, remained obscure. AdpA from S. lincolnensis (namely AdpA ) has been proved to activate lincomycin biosynthesis. Here we found that both lincomycin and melanin took l-tyrosine as precursor, and AdpA activated melanin biosynthesis as well. Three tyrosinases, MelC2, MelD2, and MelE, and one tyrosine peroxygenase, LmbB2, participated in lincomycin and melanin biosynthesis in different ways. For melanin biosynthesis, MelC2 was the only key enzyme required. For lincomycin biosynthesis, MelD2 and LmbB2 were positive factors and were suggested to convert l-tyrosine to l-dihydroxyphenylalanine (l-DOPA). Otherwise, MelC2 and MelE were negative factors for lincomycin biosynthesis and they were supposed to oxidize l-DOPA to generate melanin and certain unknown metabolite, respectively. Based on in silico analysis combined with electrophoretic mobility shift assays (EMSAs), we proved that AdpA directly interacted with promoters of melC, melD, and melE by binding to putative AdpA-binding sites in vitro. Moreover, in vivo experiments revealed that AdpA positively regulated the transcription of melC and melE, but negatively regulated melD. In conclusion, AdpA was the switch of secondary metabolism in S. lincolnensis, and it modulated precursor flux of lincomycin and melanin biosynthesis by directly activating melC, melE, and lmbB1/lmbB2 or repressing melD.