Figure 6. Torque profile of the α-actinin monomer and dimer.

Torsion was applied to the termini of both the α-actinin rod domain monomer (A–B) and dimer (C–D) using rotating constraints in NAMD [59]. Torque was applied at both termini in both the clockwise and counterclockwise directions. A) Comparison of torque needed to rotate terminus A in the clockwise (green) and counterclockwise (purple) directions. The data is plotted using window averaging. Average of torque values in each 5-degree window is plotted with the standard error shown in error bars. Rotation beyond 140 degrees in the clockwise direction shows a significant increase in torque required as compared to counterclockwise rotation. B) Window averaged plot of the rotation of terminus B in either the clockwise (green) or counterclockwise (purple) directions. Clockwise rotation beyond 140 degrees required more torque than counterclockwise rotation. C) Window averaged plot of torque required to rotate the α-actinin rod domain dimer in the clockwise (blue) or counterclockwise (red) directions at terminus A. Clockwise rotation requires less torque than counterclockwise rotation because of steric interactions resulting from rotation of R1 in the counterclockwise direction. D) Torque required to rotate the α-actinin rod domain dimer at terminus B in either the clockwise (blue) or counterclockwise (red) directions. Rotation in either direction increases the total torque required, especially passed 150 degrees because of steric interaction with the complementary monomer.