There are two families of motor proteins: Actin motors, such as myosin which move along actin microfilaments, and Microtubule motors, such as dynein and kinesin move along tubulin microtubules.

There are approximately 50 human kinesins that are currently divided into at least 14 classes. Kinesins are involved in almost all aspects of intracellular transport and their well documented role in cell division suggests that they may be excellent targets for anti-mitotic drug discovery. All kinesin proteins contain a conserved motor domain that contains a microtubule binding site and the ATP binding / hydrolysis site. The motor domain of various kinesins have been shown to have widely differing sensitivities to ATP analogs and inhibitory compounds such as monastrol, such results lead the way to the identification of therapeutically useful kinesin specific inhibitors.

Myosin motor proteins orchestrate a wide range of kinetic events within a cell. They have been shown to move cargoes such as vesicles along actin filament tracks. Myosins operate by utilizing the energy of ATP to hydrolysis, an activity that is greatly enhanced in the presence of pre-formed actin filaments.