Exploiting cryo-EM structures of actomyosin-5a to reveal the physical properties of its lever

Abstract

Myosin 5a (Myo5a) is a dimeric processive motor protein that transports cellular cargos along actin filaments. Its long lever is responsible for its large powerstroke, step size and load-bearing ability. Little is known about the levers structure and physical properties, and how they contribute to walking mechanics. Using cryo-electron microscopy and molecular dynamics simulations, we resolved the structure of monomeric Myo5a, comprising the motor domain and full-length lever, bound to F-actin. The range of its lever conformations revealed its physical properties, how stiffness varies along its length and predicts a large, 35 nm, working stroke. Thus, the newly released trail head in a dimeric Myo5a would only need to perform a small diffusive search for its new binding site on actin, and stress would only be generated across the dimer once phosphate is released from the lead head, revealing new insight into the walking behaviour of Myo5a.