Roles of protein synthesis and tRNA aminoacylation in the regulation of intracellular protein breakdown in E. coli

Abstract

The previously suggested roles of protein synthesis and tRNA aminoacylation in the regulation of intracellular protein breakdown were examined in strains of E. coli temperature-sensitive for aminoacyl-tRNA synthetases. Direct measurements of tRNA aminoacylation show no correlation between the degree of tRNA charging and the rate of protein breakdown. Protein breakdown was accelerated by transfer from 30°C to 42°C to about the same degree in temperature-sensitive mutants as in related normal strains. Deprivation of inorganic phosphate at the high temperature stimulated further protein breakdown in normal, but not in temperature-sensitive strains. It is concluded that the regulation of protein breakdown requires concomitant protein synthesis and is not influenced by the level of aminoacylation of tRNA.