Anisotropic Elasticity of the Myosin Motor in Muscle

Figures

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  Figure A1. Schematic 2D representation of an elastic element with different stiffness values of εx and εz along the x and z directions, respectively. An external force F (blue arrow) applied to the tip of the elastic element (orange circle) is equilibrated by the strains Δx and Δz, eliciting the restoring forces (yellow arrows) that balance the component of F along the x (Fx) and z (Fz) directions, respectively (white arrows).

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  Figure A2. Schematic 2D representation of an elastic element with different stiffness values of εx and εz along the x and z directions, respectively. The blue line at angle α with the z axis represents the structural constraint of the movement of the tip of the element (orange circle) when a force F (blue arrow) is applied. Red arrows: component of the force F along the constraint; green arrow: restoring forces along the constraint, at equilibrium; yellow arrows: restoring forces along the x and z axis; white arrow: projection of F along the z direction. (A) Force F parallel to the z axis. (B) Force F at a generic angle β with the z axis.

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  Figure 1. Schematic 2D representation of an elastic element with different stiffness values εx and εz along the x and z directions, respectively. The blue line at angle α with the z axis represents the structural constraint for the movement of the tip of the element (orange circle) when force F (blue arrow) is applied.

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  Figure 2. Structural model for two myosin motors, in the rigor conformation, attached to two consecutives actin monomers on the same strand of the actin helix. Gray and black: actin monomers; red and brown: myosin motors’ catalytic domain; green (light and dark): lever arm; yellow circles: pivoting points on Cys707; cyan circles: tip of the lever arm at Lys843. The Regulatory (RLC) and Essential (ELC) Light Chains wrapped around the lever arm are not shown to better visualize the lever arm’s orientation. Atomic coordinates from [16]. (A,B) Lateral views across the actin filament axis (Z axis). (C) View along the direction of the filament axis. The thin black lines represent the trajectories of the res843s when the lever arms rotate on planes containing the Z axis (axial movement).

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  Figure 3. As in Figure 2, but now with the Lys843 of the two motors forced to share the same coordinates. (A,B) Lateral views across the actin filament axis (Z axis). (C) View along the direction of the filament axis. Blue lines: constrained positions of the shared Lys843s.