Microtubule motors: many new models off the assembly line.

A far greater variety of microtubule-based motors populate the interior of most eukaryotic cells than was ever imagined, and the inventory of these proteins is growing each year. The discovery of new motors, however, has raised many questions of how cells use their arsenal of force-generating machines. The ability to apply genetics, bacterial expression, biochemistry and in vitro motility assays to study motor proteins provides new opportunities for examining these problems at a molecular level.