Figure 9.
VLN5 Caps the Barbed Ends of Actin Filaments.
(A) Preformed F-actin seeds (0.8 μM) were incubated with different concentrations of VLN5, and 1 μM G-actin, saturated with 4 μM human profilin I, was added to initiate actin elongation at the barbed end. Polymerization was monitored by tracking the increase in pyrene-actin fluorescence upon assembly. Concentrations of VLN5, from top to bottom, were 0, 9, 18.6, 93.3, 46.7, 140, 186.7, and 233 nM. A single representative experiment (n = 3) is shown.
(B) Initial rates of elongation as a function of VLN5 concentration were plotted for the representative experiment shown in (A). The data were fit with Equation 1 (see Methods) to determine an apparent Kd value of 20.4 nM for VLN5 binding to filament barbed ends.