Temporal appearance of bacteriophage T4-modified valyl tRNA synthetase in Escherichia coli.

Bacteriophage T4-induced modification of Escherichia coli vlayl-tRNA synthetase (EC 6.1.1.9) requires: synthesis of a phage-gene specified tau factor, addition of the factor to host valyl-tRNA synthetase to produce a urea-stable enzyme, and interaction of the modified enzyme with tRNA to produce a more rapidly sedimenting valyl-tRNA synthetase activity on sucrose density gradients. This report demonstrates that the coincident, chloramphenicol-sensitive appearance of urea-stable and rapidly sedimenting valyl-tRNA synthetase activity are immediate early phage functions. It implies that once the tau factor is synthesized, further interactions are stoichiometric rather than catalytic. The potential for valyl-tRNA synthetase modification accumylates when E. coli is infected with T4 PHAGE IN THE PRESENCE OF CHLORAMPHINICOL AND IS EXPRESSED DURING THE RESUMPTION OF PROTEIN SYNTHESIS WHEREAS FURTHER RNA synthesis is inhibited by rifampicin. The modification phenomenon occurs similarly in several strains of E. coli and represents a novel virus-host interaction.