The mammalian cytoskeleton is an internal framework of actin, tubulin, and intermediate filament proteins. Proteins of these three classes assemble non-covalently into filamentous polymers that support the structural integrity of the relatively fragile lipid plasma membrane. In addition, cytoskeletal polymers provide the mechanical strength that hold a cell together and anchor it to its growth substrate. The cytoskeleton must also have the capacity for rapid and substantial remodeling and provide the motive and tractor force necessary to drive motility. As such, the cytoskeleton has a...