Genetics and physiology of bacteriophage T4 3'-phosphatase: evidence for involvement of the enzyme in T4 DNA metabolism.

Mutants of bacteriophage T4D which fail to induce the deoxyribonucleotide-specific T4 3'-phosphatase have been isolated. These mutants (T4pseT) grow as well as wild-type T4 in most strains of Escherichia coli, but not in the T4-sensitive "Hospital Strain," CT196, or in a derivative strain, CTr5x. Both the formation of infectious centers and the final yield of phage are reduced by 98% when CTr5x is infected by T4pseT mutants. The growth defects are accompanied by a 50% reduction in the rate of T4 DNA synthesis, a decrease in the single-strand length of the DNA product to about one-half the mature length, and greatly reduced packaging of DNA into phage particles. Introduction of an extra-cistronic suppressor mutation (stp) into T4pseT eliminates both the requirement for the T4 3'-phosphatase in infected CTr5x and the other observed effects of the pseT mutations. The pseT gene lies between genes 63 and 31. The stp gene lies in the nonessential region between rIIB and ac. Our results suggest that 3'-phosphoryl termini can disrupt T4 DNA replication to the extent that T4 3'-phosphatase becomes required for phage production.