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Wednesday, December 14, 2011

Cooperative Responses of Multiple Kinesins to Variable and Constant Loads

D. Kenneth Jamison, Jonathan W. Driver and Michael R. Diehl

Microtubule-dependent transport is most often driven by collections of kinesins and dyneins that function in either a concerted fa-shion or antagonistically. Several lines of evi-dence suggest that cargo transport may not be influenced appreciably by the combined action of multiple kinesins. Yet, as in previous optical trapping experiments, the forces imposed on cargos will vary spatially and temporally in cells depending on a number of local environ-mental factors, and the influence of these con-ditions has been largely overlooked. Here, we characterize the dynamics of structurally-defined complexes containing multiple kinesins under controlled loads of an optical force clamp. While demonstrating that there are ge-neric kinetic barriers that restrict the ability of multiple kinesins to cooperate productively, the spatial and temporal properties of applied loads is found to play an important role in the collective dynamics of multiple-motor systems. We propose these dependencies have implica-tions for intracellular transport processes, es-pecially for bidirectional transport.

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