FIGURE 7.

Interaction between G63D actin and gelsolin and the effect of the gelsolin·G63D complex on polymerization of WT actin. A, gelsolin·WT actin complex (Gel·WT complex), gelsolin·G63D actin complex (Gel·G63D complex), or gelsolin alone was added to 1 μm RhPh-labeled rabbit skeletal muscle actin filaments (SK actin). The mixture was then diluted and visualized on HMM-coated coverslips using a fluorescence microscope. Scale bar, 10 μm. B, rates of WT actin elongation in the presence of Gel·G63D or Gel·WT complex were measured to examine the interaction between the barbed ends of WT actin and the pointed ends of G63D actin. 1 μm WT actin (15% pyrene-labeled) was allowed to polymerize in the presence of the following additives: gelsolin·G63D complex (filled triangles), gelsolin·WT actin complex (open circles), and G-buffer (open squares). Polymerization was followed by monitoring the pyrene fluorescence intensity for 60 min. The boxed area is enlarged in C.