1. MCD Biology Department, University of Colorado at Boulder, Colorado 80309-0347, USA
2. Institute of General Pathology and Pathophysiology, Moscow 125315, Russia
3. National Research Centre for Haematology, Moscow 125167, Russia
4. Physics Department, Moscow State University, Moscow 119992, Russia
5. Institute of Theoretical and Experimental Biophysics, Pushchino 142292, Russia

Correspondence to: J. Richard McIntosh¹ Correspondence and requests for materials should be addressed to R.M. (Email: richard.mcintosh@colorado.edu).

Abstract

Microtubules (MTs) are important components of the eukaryotic cytoskeleton: they contribute to cell shape and movement, as well as to the motions of organelles including mitotic chromosomes. MTs bind motor enzymes that drive many such movements, but MT dynamics can also contribute to organelle motility^{1, 2, 3, 4, 5, 6, 7, 8}. Each MT polymer is a store of chemical energy that can be used to do mechanical work, but how this energy is converted to motility remains unknown. Here we show, by conjugating glass microbeads to tubulin polymers through strong inert linkages, such as biotin–avidin, that depolymerizing MTs exert a brief tug on the beads, as measured with laser tweezers. Analysis of these interactions with a molecular-mechanical model of MT structure and force production^{9, 10} shows that a single depolymerizing MT can generate about ten times the force that is developed by a motor enzyme; thus, this mechanism might be the primary driving force for chromosome motion. Because even the simple coupler used here slows MT disassembly, physiological couplers may modulate MT dynamics in vivo.

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