Reverse branch migration of Holliday junctions by RecG protein: a new mechanism for resolution of intermediates in recombination and DNA repair

Cell. 1993 Oct 22;75(2):341-50. doi: 10.1016/0092-8674(93)80075-p.


The RecG protein of E. coli is a junction-specific DNA helicase involved in recombination and DNA repair. The function of the protein was investigated using an in vitro recombination reaction catalyzed by RecA. We show that RecG counters RecA-driven strand exchange by catalyzing branch migration of the Holliday junction in the reverse direction. This activity represents a new mechanism for resolving recombination intermediates that is independent of junction cleavage. We discuss how reverse branch migration can facilitate DNA repair, promote recombination in conjugational crosses, and confine the distribution of Chi-stimulated cross-overs. We suggest that the RecG mechanism for resolution of junctions is universal and provides a simple system that allows gene conversion without associated crossing over.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adenosine Triphosphatases / metabolism
  • Adenosine Triphosphate / metabolism
  • Bacterial Proteins / metabolism*
  • Conjugation, Genetic
  • DNA Helicases / genetics
  • DNA Helicases / metabolism
  • DNA Repair*
  • DNA, Bacterial / radiation effects
  • Escherichia coli / enzymology
  • Escherichia coli / genetics*
  • Escherichia coli Proteins*
  • F Factor
  • Models, Genetic
  • Nucleic Acid Conformation*
  • Rec A Recombinases / metabolism
  • Recombination, Genetic*
  • Structure-Activity Relationship
  • Substrate Specificity
  • Ultraviolet Rays / adverse effects


  • Bacterial Proteins
  • DNA, Bacterial
  • Escherichia coli Proteins
  • RecG protein, E coli
  • Adenosine Triphosphate
  • Rec A Recombinases
  • Adenosine Triphosphatases
  • DNA Helicases