FIGURE 4.

Budding yeast myosin-V motor activities with yeast and muscle actin isoforms. Sc-MyoV motor activity was measured using ATPase and in vitro motility assays with muscle, yeast, and mutant yeast actins. A, actin-activated Mg²⁺-ATPase activity was measured as a function of actin concentration (yeast, muscle, and the yeast 4Ac mutant). Plots were generated from average values obtained from 3–4 different datasets using at least two independent preparations of Sc-MyoV and the actins. Curves were fit using Michaelis-Menten kinetics. B, actin-activated ATPase data comparing average Sc-MyoV motor activity with 25 μm yeast, muscle, and mutant 4Ac and sub12 yeast actins (n = 3). The difference between the values for wild-type yeast (or 4Ac) and muscle (or sub12) actin are significant (p < 0.0001). C, a comparison of the average actin filament gliding rates for Sc-MyoV from in vitro motility assays using yeast, muscle, and mutant yeast actins (n = 20–40).