Pleiotropic functions of a Streptomyces pristinaespiralis autoregulator receptor in development, antibiotic biosynthesis, and expression of a superoxide dismutase

In Streptomyces, a family of related butyrolactones and their corresponding receptor proteins serve as quorum-sensing systems that can activate morpho logical development and antibiotic biosynthesis. Streptomyces pristinaespir alis contains a gene cluster encoding enzymes and regulatory proteins for t he biosynthesis of pristinamycin, a clinically important streptogramin anti biotic complex. One of these proteins, PapR1, belongs to a well known famil y of Streptomyces antibiotic regulatory proteins. Gel shift assays using cr ude cytoplasmic extracts detected SpbR, a developmentally regulated protein that bound to the papR1 promoter. SpbR was purified, and its gene was clon ed using reverse genetics. spbR encoded a 25-kDa protein similar to Strepto myces autoregulatory proteins of the butyrolactone receptor family, includi ng scbR from Streptomyces coelicolor. In Escherichia coli, purified SpbR an d ScbR produced bound sequences immediately upstream of papR1, spbR, and sc bR. SpbR DNA-binding activity was inhibited by an extracellular metabolite with chromatographic properties similar to those of the well known gamma -b utyrolactone signaling compounds. DNase I protection assays mapped the SpbR -binding site in the papR1 promoter to a sequence homologous to other known butyrolactone autoregulatory elements. A nucleotide data base search showe d that these binding motifs were primarily located upstream of genes encodi ng Streptomyces antibiotic regulatory proteins and butyrolactone receptors in various Streptomyces species. Disruption of the spbR gene in S. pristina espiralis resulted in severe defects in growth, morphological differentiati on, pristinamycin biosynthesis, and expression of a secreted superoxide dis mutase.