Polysome breakdown and the synthesis of ribonucleic acid in stringent and relaxed Escherichia coli cells starved for amino acids.

Abstract

A comparison was made of the kinetics of polysome breakdown and of the fate of RNA formed during phenylalanine starvation in both relaxed and stringent Escherichia coli cells. In the stringent strain polysome breakdown is completed within 15 min of the onset of starvation as against the 60 min required for this process in relaxed cells. In both strains phenylalanine starvation decreases the quantity of newly-formed RNA in the extract, and a constant percentage of the RNA found in the extract is always connected with the polysomes. Phenylalanine starvation does not affect the distribution of RNA between extract and pelletable membrane fractions prepared from stringent cells. In relaxed cells on the other hand, most of the RNA formed during starvation remains attached to the pelletable membrane fraction. The RNA released into extracts of starved relaxed cells is mainly 4 S RNA, with small quantities of 16 S RNA. All the 23 S RNA and most of the 16 S RNA formed during starvation remain connected with the pelletable membrane fraction.