Deoxyribonucleic acid synthesis in Escherichia coli infected with some deoxyribonucleic acid polymerase-less mutants of bacteriophage T4

Abstract

Data are presented to show that when E. coli B cells are infected by amber mutants whose mutations are located in gene 43 of bacteriophage T4, the usual phage-induced DNA polymerase (DNA nucleotidyltransferase, E.C. 2.7.7.7) activity does not appear. Instead, DNA polymerase activity decreases in extracts of E. coli B infected with these mutants, as compared to the activity present in extracts of uninfected cells. These data indicate that gene 43 of bacteriophage T4 is either the structural gene for DNA polymerase or possibly a regulator gene. The host DNA polymerase cannot overcome the deficiency of phage-induced DNA polymerase in E. coli B infected with gene 43 amber mutants. The host enzyme does not catalyze the synthesis of detectable amounts of DNA in the infected cells even though it can catalyze T4-DNA replication in vitro. One gene 3 mutant, amN101does induce a small amount of DNA synthesis in E. coli B cells after a considerable lag, but this mutant appears to be an atypical amber mutant since it replicates poorly in the usual permissive host, E. coli CR63. This limited ability of am N101 to replicate in E. coli CR63 is accompanied by defective DNA synthesis and control of early enzyme synthesis as is observed with other amber mutants in E. coli B, the nonpermissive host.