Fig. 6. Tropomyosin inhibits F-actin severing by cofilin. Rhodamine-biotin-labeled actin filaments were polymerized and attached to the surface of the perfusion chamber with anti-biotin antibody. Chambers were perfused with buffer or recombinant rat TM5a. All chambers were washed with cofilin storage buffer, and the first set of images was taken (time 0). Cofilin in the same buffer was perfused and 1 minute later another set of images was taken of the same field. Filaments saturated with TM5a did not show any severing while control filaments were severed by cofilin (arrowheads). While control fields show an increase in the number of filaments, pre-treatment of filaments with TM5a leads to the complete inhibition of this effect (right panel; a. u., arbitrary units).