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 bi osynthetic gene, strB1, is dependent on the pathway-specific activator protein StrR. We show here that StrR is a DNA-binding protein which s pecifically interacts with the strB1 promoter fragment. Footprinting e xperiments demonstrate that the StrR protein binds to an inverted repe at located upstream of the strB1 promoter. Further StrR-binding sites having the consensus sequence GTTCGActG(N)(11)CagTcGAAc were identifie d in the str-sts gene clusters of S. griseus and Streptomyces glaucesc ens by sequence comparison, gel retardation, and footprinting studies. The genetic and biochemical evidence strongly supports the model of t he StrR protein activating the expression of streptomycin biosynthetic genes by interacting with multiple binding sites within the str-sts g ene clusters of S. griseus and S. glaucescens.