Synthesis of E Colicins in Escherichia Coli

Mitomycin C treatment of Escherichia coli cells containing one of the ColE plasmids results in specific inhibition of chromosomal protein synthesis and a high rate of protein synthesis from about 35% of the plasmid genome, whereas similar treatment of plasmid-free cells has no measureable effect on protein synthesis. In the case of ColE2- and ColE3-containing cells, the antibiotic colicin protein (molecular weight about 78000) and two others (molecular weight about 11000 and 6000) are coordinately synthesized in the approximate molar ratio 1:4:1, while in ColE1-containing cells only the colicin protein is synthesized in large amounts. Partially purified colicin E2 isolated from the outer cell surface is associated with the two small proteins in the approximate molar ratio 1:1:1, indicating that not are they only synthesized coordinately but are released as a ternary complex.