Figure 2.

Actin polymerization and bundling induced by MBP-α-peptides and the effect of Ca²⁺-CaM. (A) Dependence of fluorescence enhancement caused by actin polymerization on the molar ratio of MBP-derived peptides to actin. All reactions were carried out in G-buffer at 30°C and contained 5 μM G-actin with various concentrations of α1- (solid line), α2- (dashed line), and α3- (dashed-dotted line) peptides. The α1-induced actin polymerization was probed also in the presence of DPC (dash-dot-dotted line). The mean ± SD of triplicates is shown. Data points are expressed as (F_i-F₀)/F₀, where F_i is the fluorescence intensity at different peptide/actin molar ratios and F₀ is the fluorescence intensity of 5 μM G-actin in G-buffer. (B) Time dependence of the increase in fluorescence caused by polymerization of 1.1 nmol of G-actin induced by 13.3 nmol of α1-peptide and decrease in fluorescence due to depolymerization after the addition of 13.3 nmol of Ca²⁺-CaM. (Arrows) Time of α1-peptide and CaM addition. Shown is a representative experiment (out of three replicates).