Figure 2. Real-time dynamics of ACF-catalyzed nucleosome translocation.

a, Donor fluorescence (green), acceptor fluorescence (red), and FRET (blue) traces showing the ACF-induced remodelling of a single nucleosome (n = 3 bp). ACF (6 nM) and ATP (2 µM) were added at time zero. The durations of the waiting phase and the translocation phase are denoted as t_wait and t_translocate, respectively b, Dependence of the mean t_wait value on ACF and ATP concentrations. c, Simultaneous monitoring of the binding of ACF and the remodelling of nucleosomes. (left panels) The upper trace shows the fluorescence signal from the Alexa 488-labelled ACF. The lower trace shows FRET between Cy3 and Cy5 on the nucleosome. ACF (4 nM) and ATP (20 µM) were added at the time indicated by the solid black line. The binding event of ACF (indicated by the first dashed line) further divides t_wait into two phases, t_bind and t_lag. (right panels) The distributions of t_bind and t_lag at two different ATP concentrations and 4 nM ACF. The distributions at different ATP concentrations are statistically distinct with 95% confidence for t_bind and more than 99% confidence for t_lag according to the Kolmogorov-Smirnov test. d, Dependence of the mean t_translocate value on ACF and ATP concentrations. Error bars are ± s.e.m.