Tmod1 and Tmod3 cap αsk-actin filament pointed ends similarly with α/βTM, TM5b, and TM5NM1, but Tmod3 caps αsk-actin pointed ends more weakly than Tmod1 with αTM2.
A–D, pyrene-actin polymerization kinetics depicting αsk-actin elongation from the pointed ends of CapZ-capped αsk-actin filaments in the presence of Tmod1 or Tmod3 and either α/βTM (A), TM5b (B), TM5NM1 (C), or αTM2 (D). Concentrations of proteins were: 1.8 μm G-actin (8% pyrene-labeled), 1.6 nm CapZ-F-actin seeds (1:100; 1.6 nm CapZ, 160 nm αsk-actin), and Tmods and TMs as indicated. E–H, the pointed (P) end capping activities of Tmod1 and Tmod3 calculated from initial rates of αsk-actin elongation from pointed ends of CapZ-capped actin filaments in the presence of Tmod1 or Tmod3 and either α/βTM (E), TM5b (F), TM5NM1 (G), or αTM2 (H). The pointed end capping efficiency is plotted as (1 − Rate/Control rate) × 100 (%). Thus, when rate/control rate = 0, 100% of pointed ends are capped. Data shown are mean ± S.D. (error bars) of three experiments. *, p < 0.05 (t test). AU, arbitrary units.