Effect of phage on amino acid activation

Infection of Escherichia coli NP2 with T-even phage strains is known to cause the appearance of a new valyl tRNA synthetase activity. In the present work mutant hosts possessing altered activating enzymes for phenylalanine, glycine, or histidine were employed to detect possible phage-induced modifications in the translating systems for these amino acids. The results establish that T4 has an absolute requirement for the phenylalanyl tRNA synthetase of its host, probably in an unmodified form, and that this enzyme is responsible for the incorporation of most, if not all, phenylalanine residues into phage protein. Other data suggest, less rigorously, that a similar conclusion holds for glycine and histidine.