Unique phenylalanine transfer ribonucleic acids in relaxed control Escherichia coli: genetic origin and some functional properties

Abstract

Inhibition of protein synthesis in relaxed control E. coli results in the formation of chromatographically unique isoacceptor species of phenylalanine tRNA. The genetic origin and some functional properties of the major unique species of tRNAPhe produced during leucine starvation were investigated. RNA:DNA hybridization analyses revealed that the normally occurring and major unique species of tRNAPHe are generated from DNA sequences which are identical or closely related and that there may be only 1 such sequence in the E. coli chromosome. Results from 32P pulse-chase experiments revealed that the unique tRNAPhe can be converted to a chromatographically normal form upon resumption of cell growth in fully supplemented medium. These findings, taken with earlier results which indicate that the unique species is not derived from preexisting, normally occurring species, indicate that the unique tRNAPhe is a modification-deficient form of the normal species. Comparative studies of the unique and normal phenylalanine tRNAs revealed that the unique species is aminoacylated at a much lower rate than the normal species and is only about 60% as efficient in a tRNA-dependent, poly(U)-directed protein synthesizing system.