Coding specificity of Escherichia coli leucine transfer ribonucleic acids and effect of bacteriophage T2 infection

Leucyl-transfer ribonucleic acid from Escherichia coli with and without phage T2 infection was fractionated into five components (Leu1 to Leu5) by reversed-phase chromatography. The codon specificity of each component was studied by ribosomal binding and leucine incorporation. The most probable assignments for uninfected E. coli leucine tRNA are: Leu1, CUG; Leu2, CUU, CUC; Leu3, CUA, CUG; Leu4, UUG; Leu5, UUG. The five components of E. coli leucine tRNA eight minutes after T2 infection showed codon specificity essentially similar to their E. coli counterparts, although the relative amount of Leu1 decreased and that of Leu5 increased, as previously shown. There was, however, a quantitative difference in the UUG-stimulated binding of T2 Leu5 to ribosomes. Moreover, T2 Leu5 is heterogeneous, including a component or components which respond to UUG. Complete codon assignment of T2 Leu5 cannot be made at the present time.