The Bacillus subtilis GTP binding protein Obg and regulators of the sigmaB stress response transcription factor cofractionate with ribosomes

Obg, an essential GTP binding protein of Bacillus subtilis, is necessary for stress activation of the sigmaB transcription factor. We investigated Obg's cellular associations by differential centrifugation of crude B. subtilis extracts, using an anti-Obg antibody as a probe to monitor Obg during the fractionation, and by fluorescent microscopy of a B. subtilis strain in which Obg was fused to green fluorescent protein.