Fig. 2.

Tropomyosin isoforms have distinct effects upon actin polymerizing from profilin:actin. Calf profilin:actin (10 μM) was incubated with tropomyosin isoforms (5 μM) and pyrenyl labeled β-actin (10 nM) under polymerizing salt conditions and the increase in pyrenyl fluorescence was monitored. Typically, the polymerization rate is faster (roughly 3 times) and the final steady-state level of polymerization higher in the presence of the non-muscle isoform Tm5 compared to skeletal muscle tropomyosin. Calf thymus profilin:actin was isolated as described (Schűler et al. 2006) and the tropomyosin isoforms were prepared as in (Hillberg et al. 2006; Lassing et al. 2010). Red squares, non-muscle Tm5; green triangles, profilin:actin only; blue diamonds, skeletal muscle Tm