Figure 5. Polycation-dependent motility does not require cofilin.

Conditions: 8.5 µM (20% labeled) Mg-ATP actin, 9 µM profilin, 100 nM Arp2/3, 200 nM CP, 2 µM cofilin, 4.5 µm diameter bead coated with 8.5 µM GST-WCA, low Mg²⁺ buffer as in Figure 4 supplemented with MgCl₂ as indicated. (A–B) Comet tail growth over time after the reactions start in the presence (A) and absence (B) of cofilin. The lengths of actin comet tails were recorded in each frame. Line segments represent growth of individual comet tails. Comet tail growth increased with the concentration of Mg²⁺, either in the presence or absence of cofilin. (C) Comet tail growth rates from A–B as a function of free Mg²⁺. MgCl₂ restored motility in a concentration-dependent manner in the presence or absence of cofilin. Errors bars show S.D. of tail growth rates.