Actin filaments disassemble in bursts in cofilin, coronin, and Aip1. (A) Time-lapse wide-field epifluorescence images of fluorescently labeled actin filaments in the presence of 2 μM cofilin, 1 μM coronin, 200 nM Aip1, 5 μM of actin monomer, and 2 mM ATP. Filaments shorten and disappear from the field of view. Bar, 3 μm. (B) Successive time-lapse images showing a single actin filament (f1) over time, along with kymographs drawn along the contours of representative filaments (f1–f4). The red lines on the image of f1 at t = 0 denote the contour on which the kymograph was drawn. Time is given on the x axis of the kymograph, whereas the position along the filament contour is given on the y axis. Mean integration time for a single image was 400 ms for f1–f3 and 16 ms for f4. Triangles denote endwise bursting (f1–f3); yellow triangles denote initial burst (f1–f3), red triangles denote successive proximal bursts (f1 and f2), and green triangle denotes a successive distal burst (f3). Same-side bursts occurred more frequently (78%) than opposite-side bursts (22%; P < 0.001, one-tailed z test). The square denotes internal disassembly event counted as a severing event (f3). Bar, 1 μm. (C) Histogram of filament burst size. The mean burst size was 260 subunits. (D) Histogram of waiting times between successive bursts (red), fit to a single exponential (black). Single exponential fit gave characteristic decay time of τ = 14 s.