COORDINATION OF LEVELS OF ELONGATION-FACTOR-TU, ELONGATION-FACTOR-TS, AND ELONGATION-FACTOR-G, AND RIBOSOMAL PROTEIN-S1 IN ESCHERICHIA-COLI

The amounts of the polypeptide chain elongation factors Tu, Ts, and G, and ribosomal protein S1 were assessed under various growth conditions using three independent procedures: (a) Immunoprecipitation and gel electrophoresis, (b) radioimmune assay, and (c) activity measurements. It was demonstrated that, during balanced growth of E. coli, the intracellular levels of these proteins increased in proportion to the growth rate, and the ratio of EF-Tu: EF-Ts: EF-G: protein S1 was 4-5: 1: 1: 1, at all growth rates.The effects of isoleucine starvation on the rates of synthesis of these proteins were examined using a pair of isogenic stringent and relaxed strains. The syntheses of all these proteins were found to be under the influence of stringent control.These results indicate that in E. coli the syntheses of the above four proteins are regulated in a coordinated manner and are subject to stringent control. © 1978 BY THE JOURNAL OF BIOCHEMISTRY.