Figure 1.

Effect of the 5′-ssDNA tail length on the single-turnover unwinding of forked DNA. The DNA substrates used were forked 16-bp duplexes with a fixed 15-nt 3′-ssDNA tail and varying 5′-ssDNA tails. A total of 2 nM DNA substrate with 30 nM BLM or without BLM (as a control), 1 mM ATP and 5 µM protein trap dT₅₆ were first preincubated, respectively, in three syringes in the reaction buffer A and the unwinding reaction was initiated by rapid mixing of the three solutions. (A) Kinetic time-courses. The solid lines are double-exponential fits of the data. Inset: time courses in the first 1.5 s. (B) Fast-phase, slow-phase and total amplitudes. (C) Rates of the two phases.