Profilin helps formin to steer actin monomers into the barbed ends of actin filaments.
CARLIER/ELSEVIER
Formins initiate actin filaments at various places such as filopodia, focal adhesions, and the cytokinetic ring. The authors show that when formin is alone on barbed ends, it slows filament dynamics by binding to and falling off the barbed ends. But when another actin-binding protein, profilin, is added, formin becomes a processive motor for rapid actin elongation.
The profilin/formin combination speeds polymerization two ways. First, it increases by 15-fold the on-rate of actin to barbed ends. “Electrostatic or hydrodynamic properties of formin,” suggests Carlier, “may allow profilin–actin to associate much faster at short distances than is [possible when] limited by diffusion.” This is a much faster rate than...
