Fig. 4.

The summary of nucleotide exchange experiments in skinned PM fibers from DCM–D94A, HCM–D166V, and WT mouse models. (A) The genotype-dependent distribution of the fast (P1) and slow (P2) parameters derived from the two-exponential fit at serial calcium solutions. Open symbols depict F mice, and closed symbols depict M mice. The data are mean ± SEM for N = 5 to 6 animals and n = 15 to 22 fibers per each pCa condition with significance calculated by two-way ANOVA with Tukey’s multiple comparison test: *P < 0.05 for DCM–D94A versus WT, ⁺P < 0.05 and ⁺⁺P < 0.01 for HCM–D166V versus DCM–D94A. Note the significant differences in P1 and P2 between DCM–D94A and WT mice at pCa 6 and between the two pathogenic RLC mutants at pCa 6, 5, and 4. (B) Comparison of P1 versus P2 in all three genotypes assessed at averaged calcium concentrations. Data points represent values averaged per animal at each pCa solution with one point = one animal at a certain pCa solution. Symbols of similar shapes between the genotypes indicate measurements performed at the same pCa. The data are mean ± SEM for N = no. animals with significance calculated with one-way ANOVA with Tukey’s multiple comparison test: *P < 0.05 and **P < 0.01 for mutant versus WT, ⁺P < 0.05, ⁺⁺P < 0.01, and ⁺⁺⁺⁺P < 0.0001 for DCM–D94A versus HCM–D166V. (C) The percent of myosin heads occupying the DRX versus SRX states was calculated using a correction factor of 0.44 for nonspecific mant-ATP binding (see Materials and Methods).