Myosin RLC and cMyBP-C^Ser282 phosphorylation in myofibrils from heart ventricles of WT-ELC, HCM-A57G, RCM-E143K, and Δ43 mice detected by Western blotting. (A) SDS-PAGE and sarcomeric protein phosphorylation monitored by Western blots and RLC-specific (left) or cMyBP-C–specific (right) antibodies (Aby). Phosphorylated forms of the mouse RLC and cMyBP-C (upper panels) were detected with +P-RLC_mse or +P-MyBP-C^Ser282 antibodies, while total proteins were assessed with RLC_tot (CT-1) or MyBP-C_tot antibodies (lower panels). (B) Quantification of myosin RLC and cMyBP-C^Ser282 phosphorylation in CMFs purified from WT-ELC (4 M, 3 F), HCM-A57G (3 M, 5 F), RCM-E143K (3 M, 3 F), and Δ43 (4 M, 2 F) mice. Open symbols depict female mice and closed symbols depict male mice. Data are mean ± SD and were analyzed using one-way ANOVA with Tukey’s comparison test. Significance was depicted as *, P < 0.05 and **, P < 0.01 between mutant versus WT-ELC; \$\$\$\$, P < 0.0001 for HCM-A57G versus RCM-E143K; and &&&&, P < 0.0001 for RCM-E143K versus Δ43 mice.