Fig. 3.
FEN1 cleaves cognate substrate on the first encounter. (A) Schematic depicting DNA bending followed by the incision of the 5′ flap by FEN1 in the single-molecule experiment. (B) Representative time trace (upper panel) shows DNA bending and loss of donor upon the first encounter of FEN1 with NonEQ DF-6,1Flap. The zoomed-in view (lower panel) emphasizes the dwell time of the bent state before cleavage (τbending-Flap). (C) Representative time trace of the cleavage of EQ DF-6,1Flap from the first instance of bending. (D) The NonEQ DF-6,1Flap dwell times (τbending-Flap) of N events are fitted to a gamma distribution. The average dwell time (Avg τbending-Flap) is used to determine the single turnover catalytic constant kSTO as 1/Avg τbending-Flap. (E) The dwell time distribution of EQ DF-6,1Flap. The uncertainties in Avg τbending-Flap correspond to the standard error of the mean.