Fig. 2: HCM mutations Y115H and E497D alter the actin-activated ATPase activity and actin sliding velocity of human β-cardiac myosin sS1.

a Steady-state actin-activated ATPase data for WT, Y115H and E497D sS1 ensembles. A representative dataset is shown from one side-by-side preparation of the three proteins; mean ± SD from three technical replicates at each actin concentration is plotted. The data is fit to the Michaelis–Menten equation (solid line) to determine k_cat and K_app for each myosin and the shaded area indicates the computed 95% confidence intervals. A summary of values and statistical comparisons from ATPase experiments from four independent protein preparations is provided in Supplementary Table 1. b Actin sliding velocities for WT, Y115H and E497D sS1 myosin ensembles at 23 °C. Filtered mean velocity (MVEL₂₀, see methods and Supplementary Fig. S2) measurements from 8 independent experiments across 4 protein preparations are reported, mean ± SEM is plotted; all values of velocities are given in Supplementary Table 1. A two-sample, two-sided unequal variance t-test (Welch’s t-test) was used to compare WT and each mutant (pairwise comparison: WT vs. Y115H, p ≤ 0.0001; WT vs. E497D, p = 0.0078). ** indicates p ≤ 0.01, **** indicates p ≤ 0.0001. Source data are provided as a Source Data file.