[Mutation affecting the rate of RNA-polymerase beta beta'-subunit synthesis in Escherichia coli]

As shown previously, rpoC1 temperature sensitive mutation affecting RNA polymerase beta' subunit, results in acceleration of beta beta' subunit synthesis at 42 degrees C. Also, it leads to the change in RNA polymerase sedimentation coefficient and to the reduction of RNA polymerase activity in vitro. According to the existing hypotheses, these properties of a mutant enzyme may be the cause of acceleration of synthesis of RNA polymerase in vitro. The opr1 mutation was found among Ts+ revertants of the Ts double mutant carrying rpoC1 and rif-r rpoB251 mutations. Reduction of the rate of beta beta' subunit synthesis caused by the opr1 mutation, is related to the structural changes of RNA polymerase itself. It has been shown, however, that the low activity in vitro and the altered sedimentation coefficient of the enzyme are not responsible for the accelerated synthesis of beta beta' subunits at 42 degrees C in the RpoC1 strains. Opr1 is a dominant mutation and it is located in the rpoBC region of the genetic map of Escherichia coli chromosome.