FIGURE 7.

Limiting SsbA in concert with SsbB and DprA contributes to RecA-promoted DNA strand exchange in the presence of ATP. Circular ssDNA (css; 10 μm in nt) and homologous linear dsDNA (lds; 20 μm in nt) were preincubated with increasing concentrations of SsbA (0.05, 0.1, 0.15, 0.2, and 0.25 mm) and then with decreasing SsbB (0.25, 0.2, 0.15, 0.1, and 0.05 μm) for 10 min at 37 °C in buffer A containing 2 mm ATP. Then DprA (0.1 μm) was added to the preformed SsbA·ssDNA, SsbB·ssDNA, or the SsbA·ssDNA·SsbB complex (SSB 0.3 μm) and incubated for 10 min at 37 °C. Finally, RecA (0.8 μm) was added, and the reaction was incubated for 60 min at 37 °C. The separation of the products and the symbols are those described in the legend to Fig. 6. The amounts of recombination intermediates (jm) and products (nc) are indicated as percentages and are the average values obtained from more than three independent experiments (the results given stand within a 5% standard error).