Actin-activated ATPase activity assays performed on myosin purified from left and right ventricles of Tg-A57G and Tg-Δ43 compared with Tg-WT mice (A), yielding Vmax (B) and Km (C), derived from the Michaelis–Menten equation. Four to five hearts from mice of each group of both sexes were used to generate one batch of myosin, and the assays (performed in triplicate) were repeated on two to four different batches of myosin. Data are mean ± SEM (A) or T SD (B; C) for n = 12 experiments (Tg-A57G), n = 6 experiments (Tg-Δ43), and n = 12 experiments (Tg-WT). *P < 0.05 depicting significance between Tg-WT and Tg-A57G/Tg-Δ43, and #P < 0.05 between Tg-A57G and Tg-Δ43, one-way ANOVA with Tukey’s multiple comparison test.