title: Exchange of DNA base pairs that coincides with recognition of homology promoted by E. coli RecA protein.
abstract: The unresolved mechanism by which a single strand of DNA recognizes homology in duplex DNA is central to understanding genetic recombination and repair of double-strand breaks. Using stopped-flow fluorescence we monitored strand exchange catalyzed by E. coli RecA protein, measuring simultaneously the rate of exchange of A:T base pairs and the rates of formation and dissociation of the three-stranded intermediates called synaptic complexes. The rate of exchange of A:T base pairs was indistinguishable from the rate of formation of synaptic complexes, whereas the rate of displacement of a single strand from complexes was five to ten times slower. This physical evidence shows that a subset of bases exchanges at a rate that is fast enough to account for recognition of homology. Together, several studies suggest that a mechanism governed by the dynamic structure of DNA and catalyzed by diverse enzymes underlies both recognition of homology and initiation of strand exchange.
authors.affiliation: Department of Genetics, Yale University School of Medicine, New Haven, CT 06510, USA.
authors.forename: Ewa
authors.initials: E
authors.lastname: Folta-Stogniew
authors.forename: Shawn
authors.initials: S
authors.lastname: O'Malley
authors.forename: Ravindra
authors.initials: R
authors.lastname: Gupta
authors.forename: Karen S
authors.initials: KS
authors.lastname: Anderson
authors.forename: Charles M
authors.initials: CM
authors.lastname: Radding
mesh_terms: D001482:Base Composition; D020029:Base Pairing; D001483:Base Sequence; D004269:DNA, Bacterial / Q000737:chemistry* / Q000378:metabolism*; D004277:DNA, Single-Stranded / Q000378:metabolism; D029968:Escherichia coli Proteins / Q000378:metabolism*; D007700:Kinetics; D011938:Rec A Recombinases / Q000378:metabolism*; D012689:Sequence Homology, Nucleic Acid
chemical_list: D004269:DNA, Bacterial; D004277:DNA, Single-Stranded; D029968:Escherichia coli Proteins; D011938:Rec A Recombinases