Identification of the bacteriophage T4 unf ( = alc) gene product, a protein involved in the shutoff of host transcription.

The introduction of plasmid pR386 into E. coli cells renders them restrictive to the growth of phage T4 unf ( = alc) mutants. This system has been used to isolate Unf+ revertants, which, along with the mutant parental strains, have been used to identify the unf gene product by two-dimensional gel electrophoresis. Synthesis of the unf gene product, a polypeptide of just over 18,000 daltons in size, begins within 1 min after infection and terminates at about 12 min after infection at 30 degrees. Gene dosage experiments suggest that the unf protein functions catalytically.