The force generated by a single kinesin molecule against an elastic load.
To probe the mechanism by which the motor protein kinesin moves along microtubules, we have developed a highly sensitive technique for measuring the force exerted by a single motor molecule. In this technique, one end of a microtubule is attached to the tip of a flexible glass fiber of calibrated stiffness. The other end of the microtubule makes contact with a surface sparsely coated with kinesin. By imaging the tip of the glass fiber on a photodiode detector, displacement of the microtubule by kinesin through as little as 1 nm can be detected and forces as small as 1 pN resolved. Using this force-fiber apparatus we have characterized the mechanical output of this molecular motor. The speed at which a molecule of kinesin moved along the surface of a microtubule decreased linearly as the elastic force was increased. The force required to stop a single kinesin molecule was 5.4 +/- 1.0 pN (mean +/- SD; n = 16), independent of the stiffness of the fiber, the damping from the fluid, and whether the ATP concentration was high or low.
Meyhöfer
E
E
Department of Physiology and Biophysics, University of Washington, Seattle 98195.
Howard
J
J
D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D001696:Biomechanical Phenomena; D001703:Biophysics / Q000295:instrumentation / Q000592:standards; D001923:Brain Chemistry; D002417:Cattle; D004548:Elasticity; D004553:Electric Conductivity; D016547:Kinesins / Q000502:physiology*; D008870:Microtubules / Q000502:physiology*; D009068:Movement; D011312:Pressure
D000255:Adenosine Triphosphate; D016547:Kinesins