Recombinational branch migration by the RadA/Sms paralog of RecA in Escherichia coli

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Abstract

RadA (also known as 'Sms') is a highly conserved protein, found in almost all eubacteria and plants, with sequence similarity to the RecA strand exchange protein and a role in homologous recombination. We investigate here the biochemical properties of the E. coli RadA protein and several mutant forms. RadA is a DNA-dependent ATPase, a DNA binding protein and can stimulate the branch migration phase of RecA-mediated strand transfer reactions. RadA cannot mediate synaptic pairing between homologous DNA molecules but can drive branch migration to extend the region of heteroduplex DNA, even without RecA. Unlike other branch migration factors RecG and RuvAB, RadA stimulates branch migration within the context of the RecA filament, in the direction of RecA-mediated strand exchange. We propose that RadA-mediated branch migration aids recombination by allowing the 3' invading strand to be incorporated into heteroduplex DNA and to be extended by DNA polymerases.

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Deani L Cooper

Department of Biology and Rosenstiel Basic Medical Sciences Research Center, Brandeis University, Waltham, United States

Competing interests
The authors declare that no competing interests exist.
Susan T Lovett

Department of Biology and Rosenstiel Basic Medical Sciences Research Center, Brandeis University, Waltham, United States

For correspondence
lovett@brandeis.edu

Competing interests
The authors declare that no competing interests exist.

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