Figure 4.

Nucleation of α-actin polymerization by PfActI filaments. 1 µM pyrene-labeled α-actin monomers were polymerized in the presence of 0.5 µM polymerized α-actin, the supernatant from a polymerized PfActI sample after ultracentrifugation at 434,500 g as well as 0.5 µM, 2.5 µM, and 6.25 µM polymerized PfActI. A linear fit of the first 2 min was performed on the resulting curves (Supplementary Fig. S4) and the slopes compared. Ultracentrifugation removes nucleating material from polymerized PfActI samples, and the nucleation efficiency of polymerized PfActI is lower towards α-actin than that of α-actin itself. Error bars represent standard deviation (n = 3). (a.u. = arbitrary units).