Actin filaments disassemble with similar kinetics from both ends. (A) Time-lapse images of actin filament bundles grown off fragments of L. polyphemus acrosomal processes. Filaments in the long bundle have exposed barbed ends (b), whereas filaments in the short bundle have exposed pointed ends (p). The two bundles shown were elongated from opposite ends of the same L. polyphemus acrosomal fragment. The brightness of the shorter bundle was increased relative to the longer one for ease of visualization. At 0 s, filament bundles were perfused with 2 μM cofilin, 1 μM coronin, 300 nM Aip1, 5 μM of actin monomer, and 2 mM ATP. Bar, 1 μm. (B) Total actin polymer mass in the filament bundles as a function of time measured for all bundles (red), bundles with exposed barbed ends (green), and bundles with exposed pointed ends (blue). To compare the rates of rapid disassembly, the slowly varying component of each decay curve was removed (Fig. S1; see Materials and methods). (C) Bar graph comparing decay rates for bundles with exposed barbed ends (b) with those with exposed pointed ends (p). Data represent mean and standard deviation of three independent experiments.