The regulator of streptomycin gene expression, StrR, of Streptomyces griseus is a DNA binding activator protein with multiple recognition sites.

In Streptomyces griseus the expression of at least one streptomycin biosynthetic gene, strB1, is dependent on the pathway-specific activator protein StrR. We show here that StrR is a DNA-binding protein which specifically interacts with the strB1 promoter fragment. Footprinting experiments demonstrate that the StrR protein binds to an inverted repeat located upstream of the strB1 promoter. Further StrR-binding sites having the consensus sequence GTTCGActG(N)11CagTcGAAc were identified in the str-sts gene clusters of S. griseus and Streptomyces glaucescens by sequence comparison, gel retardation, and footprinting studies. The genetic and biochemical evidence strongly supports the model of the StrR protein activating the expression of streptomycin biosynthetic genes by interacting with multiple binding sites within the str-sts gene clusters of S. griseus and S. glaucescens.