FIGURE 3:

Profilin reduces rate of bundle-mediated processive elongation. Conditions as in Figure 2 with 1 μM actin, 10 mM total Mg²⁺, 1 μM profilin, and 75 nM actin seeds. (A) Time-lapse image of sustained processive association of actin filaments on GST-PP-WWCA–coated glass nanofibers in presence of profilin. White arrowheads indicate buckling of a rapidly growing filament. Black arrowheads indicate approximate position of barbed-end attachment point. (B, C) Elongation of untethered (B) or tethered filaments (C) in 10 mM Mg²⁺. Barbed-end growth rates shown in Table 1. Scale bar, 10 μm.