EVIDENCE THAT THE BACILLUS-SUBTILIS PYRIMIDINE REGULATORY PROTEIN PYRR ACTS BY BINDING TO PYR MESSENGER-RNA AT 3 SITES IN-VIVO

The Bacillus subtilis pyr operon is regulated by a transcriptional att enuation mechanism that requires the PyrR regulatory protein, Multicop y plasmids that could be transcribed to yield segments of RNA from the attenuation regions of the pyr operon induced derepression of chromos omal pyr genes, whereas plasmids that could not yield pyr RNA did not. We conclude that pyr RNA acts by titrating the PyrR protein and preve nting it from regulating pyr attenuation.