Differential synthesis of bacteriophage-specific proteins in MS2-infected Escherichia coli treated with actinomycin

Escherichia coli pretreated with EDTA and actinomycin remained susceptible to infection with MS2, although the efficiency of infection and burst size were reduced markedly at high concentrations of actinomycin. At an optimum concentration of actinomycin the synthesis of protein and RNA was largely dependent on bacteriophage infection. Phage-specific protein synthesis was followed by measuring incorporation into protein of histidine, an amino acid not present in the phage coat protein, and arginine or lysine, which are present in the coat protein. The maximal rate of histidine incorporation into the proteins of the infected cell was reached about six minutes earlier than the maximal rate of arginine incorporation, and histidine incorporation levelled off sooner. The total number of coat protein molecules made during the replicative cycle exceeded the number of histidine residues incorporated by a factor of three to five. Protein synthesis was shown to be dependent on the formation of RNA by measuring amino acid incorporation into protein under a variety of conditions where little or no viral RNA was made. Under every such condition the incorporation of both histidine and arginine (or lysine) was inhibited. It is concluded that the protein synthesis observed occurs on newly formed RNA templates, and that the translation of different cistrons of progeny RNA is regulated with regard to time and rate.