Effect of ATP concentration on γ complex·DNA binding kinetics. Rates of DNA binding were measured as a function of ATP concentration in a reaction in which γ complex was not preincubated with ATP. A solution of γ complex and p/t-DNA-DCC was mixed with a solution of ATP, and the DCC fluorescence was measured as a function of time. Final concentrations were: 200 nm p/t-DNA-DCC and γ complex; and A, 25 μm (red trace); B, 50 μm (green trace); C, 250 μm (orange trace); and D, 500 μm (blue trace) ATP relative to the same reaction at 100 μm ATP (black trace) in assay buffer with 4% glycerol.