BUTYROLACTONE AUTOREGULATOR RECEPTOR PROTEIN (BARA) AS A TRANSCRIPTIONAL REGULATOR IN STREPTOMYCES-VIRGINIAE

BarA of Streptomyces virginiae is a specific receptor protein for virg iniae butanolides (VBs), a member of the butyrolactone autoregulators of Streptomyces species. Sequencing around the barA gene revealed two novel open reading frames: one upstream, barX, encoding a homolog of A fsA of Streptomyces griseus and another downstream, barB. Northern (RN A) blot analysis for S. virginiae demonstrated that the addition of VB during cultivation switched on the expression of barB. An in vivo exp ression system in Streptomyces lividans with the use of the xylE repor ter gene indicated that BarA in conjunction with VB controlled the bar B promoter, Furthermore, the DNA binding ability of BarA was demonstra ted in vitro for the first time by means of surface plasmon resonance and a gel-shift assay. Complex formation with VB in vitro resulted in the dissociation of BarA from DNA, thus suggesting that the VB recepto r, BarA, is a transcriptional regulator and that the VB signal is tran sduced to the next step in the signal transduction pathway by modifica tion of the DNA binding ability of BarA.