An RNA polymerase with reduced fidelity of RNA synthesis from an E. coli mutant suggests the existence of a correction system of non-complementary nucleotide incorporation during transcription.

An RNA polymerase mutant of E. coli B/r-rpoB402, with a pleiotropic effect on stability of the phenotype has recently been obtained (8-11). The present study is concerned with the fidelity of in vitro RNA synthesis carried out by highly purified RNA polymerase from the wild type strain and rpoB402 mutant. The data indicate that mutational alteration of RNA polymerase reduced the accuracy of the enzyme to a value lower than that required for the cell. The results suggest the existence of some correcting system during transcription.