Studies on the RNA polymerase in Escherichia coli K12 using the mutation affecting its activity

Abstract

RNA polymerase has been purified from the mutant ts-19 of Escherichia coli K12, which does not synthesize RNA at elevated temperatures. RNA polymerase from this strain was unable to synthesize complementary RNA on a DNA template in vitro. Studies of the complementation of the mutant polymerase with the normal E. coli polymerase inactivated by moderate heating were carried out. It has been found that mixing these two inactive polymerase preparations resulted in the appearance of DNA-dependent RNA synthesis, reaching 10 to 30% of the activity of the native enzyme. It was concluded that the mutation and heating affect different subunits of the enzyme and undamaged components can complement in vitro. Heated wild-type polymerase could also be activated by the addition of protein fraction eluted with 0.4 m-KCl from the DEAE cellulose column during standard polymerase purification. This protein was called “restoring protein”. Our results lead to the conclusion that RNA polymerase is built up of different components which can spontaneously re-associate giving active polymerase molecules: (1) the larger component with a molecular weight about 300,000, which is not inactivated by moderate heating but is affected by the mutation; and (2) smaller subunits which aro damaged by heating but are not inactivated by the mutation ts-19.