Figure 2.

Effects of mavacamten on the types of myosin heads in myofibrils.A, example transients of bovine masseter myofibrils without (open dark gray squares) and with 3 μM mavacamten (closed light gray squares). These were best described by a double exponential with a fast phase k_obs = 0.01252 s⁻¹ and a slow phase k_obs = 0.00356s⁻¹, while the fast phase amplitude of 4.9% and a slow phase amplitude of 3.4% in the presence of mavacamten. The values for k_obs are summarized in Table S1. B, mavacamten concentration dependence of the slow phase amplitude for bovine masseter myofibrils. The K_d of the mavacamten for bovine masseter myofibrils was 2.1 ± 1.2 μM. C, example transients of bovine masseter (orange closed squares), rabbit psoas (open blue squares), and porcine ventricle (crossed green squares). These were both described by double exponentials with the fast phase k_obs = 0.08922 s⁻¹ and slow phase k_obs = 0.00702 s⁻¹ with an amplitude of 3.8% and 1.7% for the fast and slow phase respectively for the rabbit psoas myofibrils. For the porcine ventricle myofibrils, the fast phase k_obs = 0.06733 s⁻¹ and the slow phase k_obs = 0.00220 s⁻¹ while the amplitudes of the fast and slow phases were 5.4% and 1.3% respectively. D, mavacamten concentration dependence of the slow phase amplitude for bovine masseter (closed orange squares), rabbit psoas (open blue squares), and porcine ventricle (crossed green squares). This gave a K_d of 14.4 ± 3.2 μM for rabbit psoas and 5.2 ± 4.2 μM for porcine ventricle. The values for k_obs are summarized in Table S1.