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.
Department of Physiology and Biophysics, University of Washington, Seattle 98195.
E
E
Meyhöfer
J
J
Howard
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