Figure 4.

Disulfide cross-linking experiments with Q41C F-actin in the absence and presence of phalloidin. Time point aliquots were taken and analyzed by SDS–PAGE. (A) SDS–PAGE of Q41C F-actin disulfide cross-linked in the absence of phalloidin. (B) SDS–PAGE of Q41C F-actin disulfide cross-linked in the presence of phalloidin. Symbols M, D, and T correspond to actin monomers, dimers, and trimers, respectively. (C) Semilogarithmic plot of disulfide cross-linking of Q41C F-actin in the absence (●) and presence (○) of phalloidin. The rates of cross-linking were determined using Sigma Plot by fitting the decreasing (with time) percentage of un-cross-linked actin monomers (from panels A and B) to a single-exponential equation. The slopes of the linear plots yielded the first-order rates of disulfide cross-linking of Q41C F-actin in the absence [k = (3.9 ± 0.09) × 10⁻² min⁻¹] and in the presence of phalloidin [k = (6.6 ± 0.1) × 10⁻² min⁻¹].