The Mechanism of Dynein Directionality

Abstract

The ability of cytoskeletal motors to move unidirectionally along filamentous tracks is central to their role in cargo transport, motility and cell division. While kinesin and myosin motor families have members that move in opposite directions, all dyneins studied to date exclusively move towards the microtubule (MT) minus-end. In order to understand the mechanism of dynein's directionality, we sought to engineer a plus-end-directed dynein guided by cryo-electron microscopy and molecular dynamics simulations. As shown by single-molecule assays, elongation or shortening of the coiled-coil stalk that connects the motor to the MT controls helical directionality of S. cerevisiae dynein around MTs. By changing the length and angle of the stalk, we successfully reversed dynein motility towards the MT plus-end. These modifications act by altering the direction dynein's linker swings relative to the MT, not by reversing the asymmetric unbinding of the motor from MT. Because the length and angle of dynein's stalk are fully conserved among species, our findings provide an explanation for why all dyneins move towards the MT minus-end.