Figure 1.

Talin ABD1 inhibits actin filament barbed-end elongation. A, barbed-end elongation was measured in the presence of 100 pm spectrin-actin seeds, 1 μm Mg-ATP–G-actin (10% pyrenyl-labeled) in the absence of talin and in the presence of 1.5 μm full-length talin, 1.5 μm ABD1, 1.5 μm ABD2, and 1.5 μm ABD3. This assay was performed at 25 mm KCl. B, barbed-end (BE) elongation was measured in the presence of 100 pm spectrin-actin seeds, 1 μm Mg-ATP–G-actin (10% pyrenyl-labeled), and increasing concentrations of ABD1 in the presence of 25 mm KCl (red points) and 100 mm KCl (blue points). Pointed end (PE) elongation was measured in the presence of 25 nm gelsolin-actin complex, 2 μm Mg-ATP–G-actin (10% pyrenyl-labeled), and increasing concentrations of ABD1 (green points). The initial rates of pointed-end and barbed-end elongation were plotted versus the concentration of ABD1. The inset shows the detail of the red curve labeled BE (25 mm KCl) between 0 and 2 μm ABD1.