Extended Data Fig. 4: Computational model parametrization and analyses.
From: Fascin structural plasticity mediates flexible actin bundle construction
a, Flowchart of the computational model. b, Atomic model of the fascin crossbridge; fiducial residues for distance calculations are indicated. Grey cylinders represent F-actin axes. c, Fascin binding probabilities as a function of inter-fiducial distances. d, Fascin binding probability as a function of the separation between the geometric center of the fiducials and the plane which spans both filament axes. e, Distribution of normalized cross-bridge energies versus the standard deviation multiplier, m, between 1 and 7. N = 2,800 independent runs. Filament A was initialized with random absolute rotation angles, while τ was varied systematically between 0.1 and 0.8 with 0.1 increments. Red line indicates median; lower and upper bounds of box are 25th and 75th percentile, respectively. Whiskers indicate range. f, Fraction of cross-bridges from simulation results in e. g, Boxplot of the distribution of normalized cross-bridge energies while varying τ using m = 4. N = 400 independent runs. F-actin A was initialized with random absolute rotation angles. Red line indicates median; lower and upper bounds of box are 25th and 75th percentile, respectively. Whiskers indicate range. h, Fraction of cross-bridges from simulation results in g. i, Heatmap of the normalized cross-bridge energies for a filament pair as a function of absolute rotation angles. White dots show energy minima. j, Plot of normalized cross-bridge energy for F-actin A rotation angle = 102.7o and varying the rotation angle of F-actin B between 60o and 140 o, with increments of 0.1o, corresponding to gray dashed line in i. k, Fascin-cross-linked filament pair for the global and local minimum indicated in j. For the global minimum, fascin is in pink (P = 0.69); For the local minimum, fascin is in red (P = 0.57). l, Heatmap of the number of cross-bridges for filament pairs with different rotational shifts. Each filament has 14 protomers. m, Representative model renderings of the minima in the upper diagonal in i, showing fascin cross-bridges in the “down” pose. n, Representative model renderings of the minima in the lower diagonal in i, showing fascin crossbridges in the “up” pose. Blue boxes indicate filament A rotation angles.
