Effect on the force–velocity relationship of lower affinity for the myosin head at the two peripheral sites in the target zone. (A) Simulations of force–velocity relationships using parameter values in Tables S1 and S2 (linear cross-bridge elasticity) assuming three sites per target zone. Data are plotted as half-sarcomere shortening velocity versus absolute force averaged over all myosin heads for either equal myosin affinity per site (filled blue symbols; same as in Fig. 2 A) or with lower affinity by 2.7 kBT (blue open symbols) for peripheral sites (shifting free energy at these sites; Fig. 1 C) by 2.7 kBT upwards. (B) The data in A are replotted after normalization. Simulation results compared with experimental data (purple) from Månsson et al. (1989).
