Decreased degradation of beta beta' RNA polymerase subunits and abnormal proteins in a mutant E. coli

An opr24 mutation decreasing the degradation of RNA polymerase beta beta' subunits was found among the Ts+ revertants of Ts strain carrying an rpoC1 mutation which stimulates overproduction of these polypeptides. The opr24 mutation is allele-non-specific, for it decreases the degradation of the mutant beta and beta' subunits, the amber-fragment of the beta subunit and the non-mutant beta' subunit. Moreover, opr24 reduces the proteolysis of abnormal proteins containing canavanine. The opr24 mutation maps between 17 and 21 min on the E. coli genetic map. The results demonstrate that a slow proteolysis rate in the bacterial cell can suppress conditional lethal mutations. In addition, the slower degradation and the ensuing accumulation of beta beta' subunits does not effect the rate of the beta beta' subunit synthesis.