Figure 4.

Effects of G-rich sequence on Pif1p binding and unwinding of downstream duplex DNA. (A) Fractions of remaining DNA molecules on coverslip decrease with time after addition of 80 nM Pif1p and 2 mM ATP. The unwinding rates for s₂₆G4d₁₇, s₂₆G4d₁₇ (Li⁺), GR₄₇d₁₇ and s₄₇d₁₇ are 0.057 s⁻¹, 0.054 s⁻¹, 0.054 s⁻¹ and 0.036 s⁻¹ by single-exponential fittings. (B) The average waiting times for the unwinding of s₄₇d₁₇, GR₄₇d₁₇, s₂₆G4d₁₇ and s₂₆G4d₁₇ (Li⁺) decrease with increasing Pif1p concentration. (C and D) The dwell time t_on for Pif1p to remain bound to ss/dsDNA with a random sequence or G-rich sequence overhang, and the time interval of two successive binding at protein concentration from 1–8 nM. t_on and t_off were obtained from single-molecule fluorescence traces in Supplementary Figure S6. Lines in (D) are the simple connections of the individual data points.