Figure 3.

Evaluating electrostatic interactions between tropomyosin and F-actin. (a) Change in the electrostatic interaction energy values for tropomyosin repositioned on F-actin in the z-direction (plot marked by x) starting from the initial reference structure (0 point on the x axis of the plot), in this case holding the rotation and azimuth of tropomyosin fixed, and for tropomyosin rotated on F-actin (plot marked by o), in this case holding the z-position and azimuth constant. Positive values for the z-position change indicate longitudinal shifting of tropomyosin toward the pointed end of F-actin, and positive values for rotation indicate a turning of tropomyosin toward the open position on F-actin. Note the strong minima in each of the plots. The z-position and rotational shifts plotted in panel a represent 2D sections through the origin in the 3D plot in panel b. (b) A plot of the electrostatic energy landscape reflecting tropomyosin movement on F-actin as a function of both z-position and pseudo-rotation (0,0 reflects the z-position and rotation of tropomyosin on F-actin in the initial reference structure). Again note the energy minima.