A mutation suppressing the overproduction of RNA polymerase beta beta' subunits in the RpoC1 strain of Escherichia coli.

Abstract

As has been shown previously, RNA polymerase β′ subunit ts-mutation rpoC1 results in an overproduction of RNA polymerase ββ′ subunits at nonpermissive temperature. The mutant enzyme shows low activity in vitro and a sedimentation coefficient 9S which is characteristic of immature core polymerase. In this paper we describe a mutation designated opr1 which suppresses RNA polymerase ββ′ subunit overproduction. The mutation was found among Ts+ revertants of the Ts double mutant carrying a rpoC1 mutation and a rif-r rpo B251 mutation. Opr1 is closely linked to the original rpo mutations and shows complete trans-dominance. Although opr1 seems to affect RNA polymerase, it does not suppress the accumulation of immature 9S RNA polymerase and does not restore the activity of the RpoC1 mutant enzyme. This and other results of a comparison of strains carrying different combinations of rpoC1, rpoB251 and opr1 mutations suggest that neither inhibition of total RNA and protein synthesis, nor the low RNA polymerase activity in vitro, nor the apparent defects in enzyme maturation, nor the enzyme degradation observed at 42°C are responsible for the ββ′ overproduction in RpoC1 strains.