Effect of bacteriophage infection upon the specificity of leucine transfer RNA for RNA codewords

Abstract

Codon responses of Leu-tRNA isolated from Escherichia coli before and after T2 phage infection were examined, using Leu-tRNA fractionated on methylated albumin-kieselguhr columns, and by binding the fractionated tRNA to ribosomes in the presence of various polynucleotides and trinucleotides. The presence of four or probably five Leu-tRNA species in uninfected E. coli is suggested. They are numbered according to their relative chromatographic mobilities. Responses of Leu-tRNA species to trinucleotides and polynucleotides can be assigned as follows: Leu-tRNA1, CUG; Leu-tRNA2, poly (U,C); Leu-tRNA3, CUU, CUC; Leu-tRNA4, poly U; and Leu-tRNA5, UUG. One minute after infection, a new Leu-tRNA species (leu-tRNAF) appears, which responds to poly UG with high efficiency, and simultaneously the amount of the tRNA1 decreases markedly. By eight minutes after infection Leu-tRNAF is no longer observed, but significant increases are observed in the response of Leu-tRNA3, Leu-tRNA4 and Leu-tRNA5 species. The differences in codon response of Leu-tRNA from E. coli before and after infection are correlated with the alteration of their elution profiles by methylated albumin-kieselguhr column chromatography. However, the biological significance of the modified tRNA remains to be determined.