Escherichia coli mutant strain with altered expression of the tryptophan operon: ribonucleic acid synthesis in vitro.

Ribonucleic acid (RNA) synthesis has been studied in vitro with a partially purified preparation of RNA polymerase from a mutant strain of Escherichia coli with a reduced rate of accumulation of tryptophan RNA (P.H. Pouwels and H.J. Scholten, J. Bacteriol. 139:393-397, 1979). The incorporation of radioactive label into RNA with polymerase from mutant bacteria is considerably lower than that with the enzyme from wild-type bacteria. These results are explained by the presence in mutant bacteria, but not in wild-type bacteria, of a factor which suppresses the accumulation of RNA. Mutant bacteria contain a factor which renders RNA synthesis with mutant and wild-type RNA polymerase resistant to various inhibitors of RNA synthesis, e.g. rifampin, streptolydigin, and heparin. We conclude that in mutant bacteria a factor is modified which suppresses the accumulation of some RNA species and lowers the sensitivity of RNA polymerase to some transcription inhibitors.