Genetically determined differences in concentrations of isoaccepting tRNAs in Escherichia coli

Two examples of genetically determined altered concentrations of isoaccepting tRNAs are presented. The concentrations of isoaccepting tRNAsThr are selectively changed by a mutation causing a fourfold overproduction of the cognate aminoacyl-tRNA-synthetase, the threonyl-tRNA synthetase, whereas the distribution of isoaccepting tRNAs of four control tRNA-species in these E. coli mutants was not affected by that mutation. Secondly evidence is presented for a correlation between mutations in structural genes of aminoacid biosynthetic enzymes and alterations in concentrations of cognate isoaccepting tRNAs in two different E. coli strains, auxotrophic for threonine, isoleucine/valine and leucine, and arginine respectively.