Obg, an essential GTP binding protein of Bacillus subtilis, is necessary for stress activation of transcription factor sigma

The general stress response sigma factor, sigmaB, of Bacillus subtilis is activated when intracellular ATP levels fall or the bacterium is exposed to environmental stress. By employing the yeast dihybrid selection to identify B. subtilis proteins that could interact with Rsb proteins and act as mediators of stress signaling, the G protein Obg was isolated as an interactor with several of these regulators. B. subtilis depleted of Obg no longer activated sigmaB in response to environmental stress.