FIGURE 2.

Fimbrin is stably associated with actin filament bundles. Determination of the fimbrin off-rate from single filaments and bundles is shown. A, a solution of 0.1 μm TMR-fimbrin was washed over single actin filaments (black). A single exponential curve fit is in black. The dissociation constant measured from this experiment was 0.043 ± 0.001 s⁻¹. Single filaments coated with TMR-fimbrin were washed with observation buffer (red). Fimbrin dissociated with an off-rate of 0.043 ± 0.001 s⁻¹. B, TMR-Fimbrin bundles were washed with different concentrations of unlabeled fimbrin: 1 μm (blue, k_off = 0.023 ± 0.003 s⁻¹), 5 μm (green, k_off = 0.025 ± 0.001 s⁻¹), 10 μm (orange, k_off = 0.025 ± 0.003 s⁻¹), 20 μm Fim1 (magenta, k_off = 0.028 ± 0.001 s⁻¹), and no significant TMR-fimbrin dissociation with buffer only (red, k_off = 0.0028 ± 0.002 s⁻¹).