Figure 6.

Schematic summary of filament bundling and formin anchoring impact on formin activity.Depending on filaments being bundled by fascin or not, and whether formin translational or rotational freedom are blocked or not, formin-induced actin filament elongation and formin detachment rate are differently affected. Top, left: a single filament elongated by an unanchored formin is chosen as the reference for the comparison of elongation rates (V_elong) and formin detachment rates (k_off). Bottom, left: when fascin bundles filaments, the activity of the formin elongating the leading filament is unaffected, whereas the elongation rate is reduced and the detachment rate is increased for formins elongating trailing filaments. Top, right: the activity of surface-anchored formins elongating individual filaments is not affected by anchoring, except in the case of a short formin-to-surface distance. Bottom, right: Simultaneously blocking filament rotation by fascin-induced bundling and formin rotational or translational freedom, strongly impacts both formin elongation rate and detachment rate, for both leading and trailing filaments.