Interactions of gene 2.5 protein and DNA polymerase of bacteriophage T7

J Biol Chem. 1992 Jul 25;267(21):15032-40.


Bacteriophage T7 gene 2.5 protein has been shown to interact with T7 DNA polymerase (the complex of T7 gene 5 protein and Escherichia coli thioredoxin) by affinity chromatography and fluorescence emission anisotropy. T7 DNA polymerase binds specifically to a resin coupled to gene 2.5 protein and elutes from the resin when the ionic strength of the buffer is raised to 250 mM NaCl. In contrast, T7 gene 5 protein alone binds more weakly to gene 2.5 protein, eluting when the ionic strength of the buffer is 50 mM NaCl. Thioredoxin does not bind to gene 2.5 protein. Steady-state fluorescence emission anisotropy gives a dissociation constant of 1.1 +/- 0.2 microM for the complex of gene 2.5 protein and T7 DNA polymerase, with a ratio of gene 2.5 protein to T7 DNA polymerase in the complex of 1:1. Nanosecond emission anisotropic analysis suggests that the complex contains one monomer each of gene 2.5 protein, gene 5 protein, and thioredoxin. The ability of T7 gene 2.5 protein to stimulate the activity and processivity of T7 DNA polymerase is compared with the ability of three other single-stranded DNA-binding proteins: E. coli single-stranded DNA-binding protein, T4 gene 32 protein, and E. coli recA protein. All except E. coli recA protein stimulate the activity and processivity of T7 DNA polymerase; E. coli recA protein inhibits these activities.

Publication types

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

MeSH terms

  • Base Sequence
  • Chromatography, Affinity
  • DNA, Single-Stranded / metabolism
  • DNA, Viral / biosynthesis
  • DNA-Binding Proteins / metabolism*
  • DNA-Directed DNA Polymerase / metabolism*
  • Fluorescence Polarization
  • Genes, Viral
  • Molecular Sequence Data
  • Osmolar Concentration
  • T-Phages / enzymology*
  • T-Phages / genetics
  • T-Phages / metabolism
  • Viral Proteins / metabolism*


  • DNA, Single-Stranded
  • DNA, Viral
  • DNA-Binding Proteins
  • Viral Proteins
  • DNA-Directed DNA Polymerase