Sarcomere Lattice Geometry Influences Cooperative Myosin Binding in Muscle
Figure 9
Steady-State Predictions Vary with Lattice Stiffness and [Ca2+]
Contour plots of average steady-state predictions from the multi-filament model for force (A–F), fractional cross-bridge binding, fxb (G–L), and cross-bridge turnover (or ATP consumption, [M–R]) as a function of [Ca2+], kxb, and filament stiffness, kF (simultaneously scaling both thick- and thin-filament stiffness using X as in Figure 8C). Within each panel, values of pCa range from 9–4, while kF values are identical to those in Figure 8C. kxb increases from left to right across each column of panels as indicated (ranging from 1–15 pN nm−1). Contour levels are specified by the color bar at the far right of each row. Areas appearing brown indicate regions where steady-state values exceed the upper limit of the color bar. The solid white circle in each panel corresponds to the maximum contour level, not a single maximum point in pCa-log10XkF−kxb space. The maximum force contour for (A–F) is 683, 766, 897, 949, 885, and 940 pN. Maximal fractional binding is 0.24, 0.18, 0.17, 0.16, 0.14, and 0.13 for (G–L), and maximal ATP consumption is 14.4, 8.57, 6.81, 5.89, 4.58, and 3.74 ATP s−1 myosin−1 for (M–R).