Figure 4.
Effect of RecUK56A or RecUR71A on RecA-mediated DNA strand exchange. (A) Circular ssDNA (10 μM) and homologous linear dsDNA (20 μM) were incubated with RecA (1.3 μM) in buffer A containing 10 mM MgOAc2 and 2 mM dATP for 30 min at 37°C. Then a RecU variant (200 nM) was added, and the reaction mixture was incubated for further 30 min at 37°C. After deproteinization, the reaction mixtures were analyzed by 0.8% agarose gel electrophoresis. In lane 3, the reaction was stopped after the first 30 min of incubation as indicated. (B) The same experiment was performed with circular ssDNA and homologous 3′-tailed dsDNA. C, partially nicked dsDNA; css, circular ssDNA; lds, linear dsDNA; nc, nicked circular DNA; jm, joint molecules; ccc, covalently closed circular DNA.