Figure 3
From: The molecular basis of thin filament activation: from single molecule to muscle
The model reproduces the Ca++-dependence of the maximum force, lifetime and frequency of binding events measured using a laser trap with a mini myosin ensemble. (a) The model reproduces the distribution of maximum forces (top) and lifetimes (bottom) of binding events at four different Ca++ concentrations. In each plot, histograms from the model (hollow circles) are superimposed over histograms from our measurements (gray). Each inset shows the maximum force and lifetime of every event as a dot. The model (bottom, red) reproduces the correlation between these two quantities observed in our measurements (top, blue). (b) The model reproduces the frequency of binding events. Data, measured over a 10 s interval, are shown as box and whisker plots, the average event frequency is shown for the model (hollow circles). Note that, because of the temporal resolution of the laser trap, the binding frequency is likely an underestimate of the true frequency. This effect is taken into account in the model to ensure a fair comparison between simulation and measurement. (c) Single molecule myosin binding frequency (ε), predicted by fitting the model to the mini-ensemble measurements (dashed line), agrees with our direct, single molecule trap measurements (data, red squares; error bars, SD; best fit, solid line). Parameters used in these simulations were N M = 14, k a2 = 36 s−1 and K = 0.2 μM. ATP concentration is 100 μM.
