A gene of bacteriophage T4 controlling the modification of host valyl-tRNA synthetase

Two hydroxylamine-induced mutants of bacteriophage T4 defective in modification of host valyl-tRNA synthetase have been isolated by assay of crude extracts for the activity that is characteristic of the wild-type virus. The mutations define a single gene that is situated between the rI and e genes on the T4 genetic map. This new gene is designated vs for valyl-tRNA synthetase. One of the mutations may be of the missense type since it results in the production of a valyl-tRNA synthetase activity that has unusual urea-inactivation properties. The other appears to be an amber mutation since the viral enzyme can only be found after infection of cells that are permissive for amber mutations. No differences in growth properties were found between wild type and amber mutant strains on the nonpermissive host. We conclude that the bacteriophage T4 valyl-tRNA synthetase is not essential for viability under prevailing laboratory conditions.