The control of ribonucleic acid synthesis during amino acid deprivation in Escherichia coli.

The rate of RNA synthesis in a stringent strain of Escherichia coli was measured before and during amino acid deprivation. Upon amino acid deprivation the rate of RNA synthesis rapidly fell to 30% of the control rate and did not significantly change from that value upon prolonged starvation. The composition of RNA synthesized during amino acid deprivation was investigated by hybridization-competition, methyl labeling with 14C-methyl-labeled methionine, and polyacrylamide-agarose gel electrophoresis. Of the RNA pulse labeled during amino acid deprivation, ribosomal and transfer species comprise about 12% of the total, as opposed to about 40% in the unstarved control. Consequently, although some ribosomal and transfer RNAs are synthesized during amino acid starvation, the RNA is considerably enriched in messenger RNA, and the major effect of amino acid deprivation is the preferential curtailment of stable RNA synthesis. Our results also indicate that the rate of messenger RNA synthesis is reduced to 50 % during amino acid deprivation.