FIGURE 7.

Cartoon depiction of the results of single-molecule TIRF and low-density and high-density motor decoration on motility in vitro. Single molecules of kinesin mostly pass and dissociate, whereas single dynein-dynactin complexes can pass, pause, dissociate, switch, and reverse direction (left column). Adding the complexity of a bead cargo with very few motors (middle column) allows kinesin to pass but also to switch frequently. Dynein-dynactin bound to beads at low density allows similar actions, with less passing on an underpass and more pausing, but also some reversing and switching (middle column). Increasing the density of bound kinesin does not significantly change the actions of cargo at intersections, but increasing the density of dynein-dynactin causes all cargo to become tethered at intersections (right column). Wavy lines denote lateral wobbling of the dynein-dynactin bead cargo.