Characterization of three positive regulators for tetramycin biosynthesis in Streptomyces ahygroscopicus.

Three putative regulatory genes, namely ttmRI, ttmRII and ttmRIII, which are present in the tetramycin (ttm) biosynthetic gene cluster, were found in Streptomyces ahygroscopicus. Disruption of ttmRI, ttmRII or ttmRIII reduced tetramycin production, and their complementation restored production to varying degrees. Gene expression analysis of the wild-type (WT) and mutant strains through reverse transcriptase-polymerase chain reaction (RT-PCR) of the ttm gene cluster showed that the expression levels of most of the biosynthetic genes were reduced in ΔttmRI, ΔttmRII and ΔttmRIII. Electrophoretic mobility shift assays demonstrated that TtmRI, TtmRII and TtmRIII bound the promoters of several genes in the ttm gene cluster. This study found that these three proteins are a group of positive regulators that activate the transcription of the ttm gene cluster in S. ahygroscopicus. In addition, AttmRII had a reduced degree of grey pigmentation. Thus, TtmRII has a pleiotropic regulatory function in the tetramycin biosynthetic pathway and in development. [ABSTRACT FROM AUTHOR]