SINGLE CYTOPLASMIC DYNEIN MOLECULE MOVEMENTS - CHARACTERIZATION AND COMPARISON WITH KINESIN

Cytoplasmic dynein is a major microtubule motor for minus-end directed movements including retrograde axonal transport. To better understand the mechanism by which cytoplasmic dynein converts ATP energy into mo tility, we have analyzed the nanometer-level displacements of latex be ads coated with low numbers of cytoplasmic dynein molecules. Cytoplasm ic dynein-coated beads exhibited greater lateral movements among micro tubule protofilaments (ave. 5.1 times/mu m of displacement) compared w ith kinesin (ave. 0.9 times/mu m). In addition, dynein moved rearward up to 100 nm over several hundred milliseconds, often in correlation w ith off-axis movements from one protofilament to another. We suggest t hat single molecules of cytoplasmic dynein move the beads because 1) t here is a linear dependence of bead motility on dynein/bead ratio, 2) the binding of beads to microtubules studied by laser tweezers is best fit by a first-order Poisson, and 3) the run length histogram of dyne in beads follows a first-order decay. At the cellular level, the great er disorder of cytoplasmic dynein movements may facilitate transport b y decreasing the duration of collisions between kinesin and cytoplasmi c dynein-powered vesicles.