FIGURE 8.

Limiting dATP concentrations facilitate RecA·ATP NPF formation and DNA strand exchange. A, circular 3,199-nt ssDNA (10 μm in nt) was incubated with RecA (0.8 μm) in buffer A containing a total of 5 mm of dATP/ATP at different ratios (5:0, 4:1, 1:1, 1:4, or 0:5) at 37 °C, and the ssDNA-dependent (d)ATPase activity was measured for 30 min. The amount of nucleotide hydrolyzed was calculated as described in the legend to Fig. 3. B, circular ssDNA (10 μm in nt) and homologous linear dsDNA (20 μm in nt) were incubated with RecA (0.8 μm) for 60 min at 37 °C in buffer A containing a total of 5 mm of dATP/ATP at different ratios (5:0, 4:1, 3:2, 1:1, 2:3, 1:4, or 0:5). The separation of the products and the symbols are those described in the legend to Fig. 6. The amount 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).