Table of Contents
Journal of Biophysics
Volume 2015, Article ID 465693, 9 pages
Research Article

Flexural Stiffness of Myosin Va Subdomains as Measured from Tethered Particle Motion

1Department of Molecular Physiology and Biophysics, University of Vermont, Burlington, VT 05405, USA
2Department of Mechanical & Aeronautical Engineering, Clarkson University, Potsdam, NY 13699, USA

Received 25 August 2015; Revised 29 October 2015; Accepted 8 November 2015

Academic Editor: Andrei B. Rubin

Copyright © 2015 Arthur J. Michalek et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


Myosin Va (MyoVa) is a processive molecular motor involved in intracellular cargo transport on the actin cytoskeleton. The motor’s processivity and ability to navigate actin intersections are believed to be governed by the stiffness of various parts of the motor’s structure. Specifically, changes in calcium may regulate motor processivity by altering the motor’s lever arm stiffness and thus its interhead communication. In order to measure the flexural stiffness of MyoVa subdomains, we use tethered particle microscopy, which relates the Brownian motion of fluorescent quantum dots, which are attached to various single- and double-headed MyoVa constructs bound to actin in rigor, to the motor’s flexural stiffness. Based on these measurements, the MyoVa lever arm and coiled-coil rod domain have comparable flexural stiffness (0.034 pN/nm). Upon addition of calcium, the lever arm stiffness is reduced 40% as a result of calmodulins potentially dissociating from the lever arm. In addition, the flexural stiffness of the full-length MyoVa construct is an order of magnitude less stiff than both a single lever arm and the coiled-coil rod. This suggests that the MyoVa lever arm-rod junction provides a flexible hinge that would allow the motor to maneuver cargo through the complex intracellular actin network.