Defining the roles of individual residues in the single-stranded DNA binding site of PcrA helicase

Proc Natl Acad Sci U S A. 2001 Jul 17;98(15):8381-7. doi: 10.1073/pnas.131009598.


Crystal structures and biochemical analyses of PcrA helicase provide evidence for a model for processive DNA unwinding that involves coupling of single-stranded DNA (ssDNA) tracking to a duplex destabilization activity. The DNA tracking model invokes ATP-dependent flipping of bases between several pockets on the enzyme formed by conserved aromatic amino acid residues. We have used site-directed mutagenesis to confirm the requirement of all of these residues for helicase activity. We also demonstrate that the duplex unwinding defects correlate with an inability of certain mutant proteins to translocate effectively on ssDNA. Moreover, the results define an essential triad of residues within the ssDNA binding site that comprise the ATP-driven DNA motor itself.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adenosine Triphosphate / metabolism
  • Bacterial Proteins / chemistry
  • Bacterial Proteins / genetics
  • Bacterial Proteins / physiology*
  • Binding Sites
  • DNA / metabolism
  • DNA Helicases / chemistry
  • DNA Helicases / genetics
  • DNA Helicases / physiology*
  • DNA, Single-Stranded / metabolism*
  • Hydrolysis
  • Models, Molecular
  • Mutagenesis, Site-Directed
  • Nucleic Acid Conformation
  • Protein Structure, Secondary


  • Bacterial Proteins
  • DNA, Single-Stranded
  • pcrA protein, Bacteria
  • Adenosine Triphosphate
  • DNA
  • DNA Helicases