Fig. 3. Effect of plectin-ABD on actin polymerization. (A) -skeletal muscle actin (4 µM) containing 10% of pyrene-labeled actin was polymerized in the presence of increasing concentrations of MBP-plectin-ABD_1-339 (squares, 0 nM; triangles, 30 nM; diamonds, 150 nM; circles, 300 nM). Actin polymerization was initiated at time 0 by the addition of 0.1 volume of 10x initiation mix and fluorescence was recorded at 407 nm using an excitation wavelength of 365 nm. (B) Actin polymerization was monitored by light scattering at 300 nm. Polymerization of 2 µM -skeletal muscle actin in the absence (squares) and presence of varying concentrations of MBP-plectin-ABD, 0.5 µM (triangles), 1 µM (diamonds) was initiated at time 0 by the addition of 0.1 volume of 10x initiation mix.