UMF: Uniform Magnetic Force; a technique used to Slow Multiple Kinesin Motors in vitro

Abstract

Can molecular motors pulling on the same load interact with each other to move faster than any one motor could? While the force generated by a single kinesin motor on a cargo in vitro has been studied extensively, the force generated by multiple kinesin motors in vitro has not been characterized as well. Using a novel Uniform Magnetic Force (UMF) apparatus, we are able to apply constant, computer controlled, uniform force over a large sample area, as opposed to a force dependent on distance from the magnetic pole. The UMF can be turned on and off rapidly, and acts upon a superparamagnetic bead bound to a microtubule through a biotin-streptavidin linkage, causing a force on the microtubule. Using Invitrogen M270 beads this force can be as high as 9pN. We employ our apparatus to investigate the velocities of microtubules being pulled by kinesin motors against a magnetic force. With a force on the order of the stall force for one kinesin we are able to see changes in the velocity of a microtubule-bead complex being pulled by kinesin motor proteins. The relative amount of velocity change is not constant for each microtubule-bead complex. This may show a dependence of velocity decrease due to the number of motors moving the microtubule.