Measurement of Force-Dependent Release Rates of Cytoskeletal Motors.

Optical tweezers permit measuring motor-filament rupture forces with piconewton sensitivity. For deeper structural and mechanistic understanding of motors, different structural constraints can be induced by pulling motor proteins at various positions and manipulating the direction of the exerted force. Here, we present an optical-trapping approach to investigate the effect of the magnitude and direction of tension applied to the linker element of cytoskeletal motors on motor-filament interactions. Using this approach, force-dependent microtubule release rates of monomeric kinesins can be directly measured by pulling on kinesin's "neck linker" with a constant force.