Figure 2.
AtCAP1 changes the critical concentration (Cc) for actin assembly. (A) Representative experiment showed that AtCAP1 changes the steady state Cc for rabbit muscle actin assembly. Increasing concentrations of 1:200 gelsolin:actin (5% pyrene labeled) was polymerized in the absence (squares) and presence (circles) of 1 μM AtCAP1. The Cc values (intercept of line of best fit with the x-axis) were 0.5 μM for actin alone and 0.9 μM with AtCAP1. The resulting Kd value for this experiment was 0.8 μM. (B) Representative experiment performed with maize pollen actin, in the presence of gelsolin to cap filament barbed ends, gives Cc values of 1 μM for actin alone (squares) and 1.4 μM with AtCAP1 (circles), with a resulting Kd = 0.3 μM. a.u., arbitrary fluorescence units.