Bidirectional stepping of cytoplasmic dynein: Effects of mechanical load and ATP hydrolysis

PHYS 6

Arne Gennerich, gennerich@cmp.ucsf.edu1, Andrew Carter1, Sam Reck-Peterson1, and Ronald D. Vale, vale@phy.ucsf.edu2. (1) Department of Cellular and Molecular Pharmacology, University of California San Francisco, 600 16th Street, San Francisco, CA 94143-2200, (2) HHMI, Department of Cellular and Molecular Pharmacology, University of California, San Francisco, San Francisco, CA 94122
Cytoplasmic dynein is a microtubule motor whose molecular mechanism of movement remains poorly understood. Here we explore the stepping behavior of yeast cytoplasmic dynein by optical trapping microscopy. At low loads, dynein advances primarily in 8 nm increments but occasionally takes much larger steps. Increasing load weakens dynein's directional bias, causing a mixture of forward and backward steps. At loads above dynein's stall force (>7 pN), the motor walks backward towards the microtubule plus-end. Remarkably, in the absence of ATP, an applied force causes dynein to step in either direction along microtubules. However, significantly less force is required to induce nucleotide-independent stepping in the minus-end direction. These findings reveal that mechanical force can drive cycles of microtubule detachment-attachment of dynein's motor domains without nucleotide hydrolysis. The inherent asymmetry in this force-induced stepping suggests a model for how dynein coordinates the activities of its two motor domains during normal processive motility.
 

Single Molecule Spectroscopy, Imaging and Manipulation of Biomolecular Systems
8:20 AM-12:00 PM, Sunday, August 19, 2007 BCEC -- 157A, Oral

Division of Physical Chemistry

The 234th ACS National Meeting, Boston, MA, August 19-23, 2007