The stretched DNA geometry of recombination and repair nucleoprotein filaments

Scott F. Singleton, Jie Xiao

Research output: Contribution to journalReview articlepeer-review


The RecA protein of Escherichia coli plays essential roles in homologous recombination and restarting stalled DNA replication forks. In vitro, the protein mediates DNA strand exchange between single-stranded (ssDNA) and homologous double-stranded DNA (dsDNA) molecules that serves as a model system for the in vivo processes. To date, no high-resolution structure of the key intermediate, comprised of three DNA strands simultaneously bound to a RecA filament (RecA·tsDNA complex), has been elucidated by classical methods. Here we review the systematic characterization of the helical geometries of the three DNA strands of the RecA·tsDNA complex using fluorescence resonance energy transfer (FRET) under physiologically relevant solution conditions. Measurements of the helical parameters for the RecA·tsDNA complex are consistent with the hypothesis that this complex is a late, poststrand-exchange intermediate with the outgoing strand shifted by about three base pairs with respect to its registry with the incoming and complementary strands. All three strands in the RecA·tsDNA complex adopt extended and unwound conformations similar to those of RecA-bound ssDNA and dsDNA.

Original languageEnglish (US)
Pages (from-to)145-158
Number of pages14
Issue number3
StatePublished - 2001
Externally publishedYes


  • DNA repair
  • Fluorescence resonance energy transfer
  • Homologous recombination
  • Homology recognition
  • Minor groove
  • RecA

ASJC Scopus subject areas

  • Biophysics
  • Biochemistry
  • Biomaterials
  • Organic Chemistry


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