The T4 phage UvsW protein contains both DNA unwinding and strand annealing activities

J Biol Chem. 2007 Jan 5;282(1):407-16. doi: 10.1074/jbc.M608153200. Epub 2006 Nov 8.


UvsW protein belongs to the SF2 helicase family and is one of three helicases found in T4 phage. UvsW governs the transition from origin-dependent to origin-independent replication through the dissociation of R-loops located at the T4 origins of replication. Additionally, in vivo evidence indicates that UvsW plays a role in recombination-dependent replication and/or DNA repair. Here, the biochemical properties of UvsW helicase are described. UvsW is a 3' to 5' helicase that unwinds a wide variety of substrates, including those resembling stalled replication forks and recombination intermediates. UvsW also contains a potent single-strand DNA annealing activity that is enhanced by ATP hydrolysis but does not require it. The annealing activity is inhibited by the non-hydrolysable ATP analog (adenosine 5'-O-(thiotriphosphate)), T4 single-stranded DNA-binding protein (gp32), or a small 8.8-kDa polypeptide (UvsW.1). Fluorescence resonance energy transfer experiments indicate that UvsW and UvsW.1 form a complex, suggesting that the UvsW helicase may exist as a heterodimer in vivo. Fusion of UvsW and UvsW.1 results in a 68-kDa protein having nearly identical properties as the UvsW-UvsW.1 complex, indicating that the binding locus of UvsW.1 is close to the C terminus of UvsW. The biochemical properties of UvsW are similar to the RecQ protein family and suggest that the annealing activity of these helicases may also be modulated by protein-protein interactions. The dual activities of UvsW are well suited for the DNA repair pathways described for leading strand lesion bypass and synthesis-dependent strand annealing.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Adenosine Triphosphate / chemistry
  • Bacteriophage T4 / chemistry*
  • Base Sequence
  • Cloning, Molecular
  • DNA Helicases / chemistry*
  • DNA Helicases / physiology*
  • DNA Repair
  • Fluorescence Resonance Energy Transfer
  • Hydrolysis
  • Models, Molecular
  • Molecular Sequence Data
  • Protein Binding
  • Protein Conformation
  • Protein Denaturation
  • Protein Structure, Tertiary
  • Recombination, Genetic
  • Viral Proteins / chemistry*
  • Viral Proteins / physiology*


  • Viral Proteins
  • Adenosine Triphosphate
  • DNA Helicases
  • UvsW protein, Bacteriophage T4