Movie 2.

The formin mDia1 can nucleate and rapidly elongate β- and γ-actin filaments. TIRF movies of reactions containing labeled combinations of 1 μM α-actin, β-actin, or γ-actin (10% Alexa-488 RMA), 10 nM mDia1(FH1-C), and 2 μM profilin-1. Scale bar, 20 μm. Playback, 10 fps.