Structure of the gene 2.5 protein, a single-stranded DNA binding protein encoded by bacteriophage T7

Proc Natl Acad Sci U S A. 2001 Aug 14;98(17):9557-62. doi: 10.1073/pnas.171317698. Epub 2001 Jul 31.


The gene 2.5 protein (gp2.5) of bacteriophage T7 is a single-stranded DNA (ssDNA) binding protein that has essential roles in DNA replication and recombination. In addition to binding DNA, gp2.5 physically interacts with T7 DNA polymerase and T7 primase-helicase during replication to coordinate events at the replication fork. We have determined a 1.9-A crystal structure of gp2.5 and show that it has a conserved OB-fold (oligosaccharide/oligonucleotide binding fold) that is well adapted for interactions with ssDNA. Superposition of the OB-folds of gp2.5 and other ssDNA binding proteins reveals a conserved patch of aromatic residues that stack against the bases of ssDNA in the other crystal structures, suggesting that gp2.5 binds to ssDNA in a similar manner. An acidic C-terminal extension of the gp2.5 protein, which is required for dimer formation and for interactions with the T7 DNA polymerase and the primase-helicase, appears to be flexible and may act as a switch that modulates the DNA binding affinity of gp2.5.

Publication types

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

MeSH terms

  • Amino Acid Sequence
  • Bacteriophage T7 / genetics
  • Bacteriophage T7 / metabolism*
  • Binding Sites
  • Crystallography, X-Ray
  • DNA, Single-Stranded / metabolism
  • DNA-Binding Proteins / chemistry*
  • DNA-Binding Proteins / genetics
  • Models, Molecular
  • Molecular Sequence Data
  • Protein Conformation
  • Sequence Alignment
  • Sequence Homology, Amino Acid
  • Viral Proteins / chemistry*
  • Viral Proteins / genetics


  • DNA, Single-Stranded
  • DNA-Binding Proteins
  • Viral Proteins
  • gene 2.5 protein, Enterobacteria phage T7

Associated data

  • PDB/1JE5