Bacteriophage T7 deoxyribonucleic acid replication invitro. Bacteriophage T7 DNA polymerase: an an emzyme composed of phage- and host-specific subunits

J Biol Chem. 1975 Jul 25;250(14):5515-22.


The DNA polymerase induced after infection of Escherichia coli by phage T7 has been purified 500-fold to near homogeneity as judged by polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate. The purified enzyme complements extracts of cells infected with a T7 gene 5 mutant to permit cell-free replication of duplex T7 DNA. In contrast, purified T4 DNA polymerase or E. coli DNA polymerase I is unable to do so, thus suggesting a specific requirement for the T7 enzyme in the replication of the viral DNA. E. coli TsnC protein is present in purified T7 DNA polymerase in one-to-one stoichiometry with T7 gene 5 protein, and can be isolated in homogeneous form from heat-denatured enzyme by chromatography on DEAE-cellulose. The inactive form of T7 gene 5 protein that accumulates in tsnC hosts has been partially purified. When partially purified gene 5 protein is mixed with purified TsnC protein, DNA polymerase activity is restored, and formation of a one-to-one complex between the two proteins occurs. These results indicate that the functional form ofT7 DNA polymerase is a complex composed of phage- and host-specified subunits.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Bacterial Proteins / pharmacology
  • Chromatography, Affinity
  • Chromatography, DEAE-Cellulose
  • Coliphages / metabolism*
  • DNA Nucleotidyltransferases / isolation & purification
  • DNA Nucleotidyltransferases / metabolism*
  • DNA Replication*
  • Deoxyribonucleotides / metabolism
  • Electrophoresis, Polyacrylamide Gel
  • Escherichia coli / metabolism*
  • Mutation
  • Sodium Dodecyl Sulfate
  • Thioredoxins / pharmacology


  • Bacterial Proteins
  • Deoxyribonucleotides
  • Sodium Dodecyl Sulfate
  • Thioredoxins
  • DNA Nucleotidyltransferases