Valyl-tRNA synthetase modification-dependent restriction of bacteriophage T4.

A strain of Escherichia coli, CP 790302, severely restricts the growth of wild-type bacteriophage T4. In broth culture, most infections of single cells are abortive, although a few infected cells exhibit reduced burst sizes. In contrast, bacteriophage T4 mutants impaired in the ability to modify valyl-tRNA synthetase develop normally on this strain. Biochemical evidence indicates that the phage-modified valyl-tRNA synthetase in CP 790302 is different from that previously described. Although the enzyme is able to support normal protein synthesis, a disproportionate amount of phage structural protein (serum blocking power) fails to mature into particles of the appropriate density. The results with host strain CP 790302 are consistent with either a gratuitous inhibition of phage assembly by faulty modification or abrogation of an unknown role that valyl-tRNA synthetase might normally play in viral assembly.