Kinesin: Directional properties, strain coordination and nanotechnology applications

Kinesin motors are biological motor proteins that evolved for a range of biological transport functions in cells. Kinesin's small size and robustness of movement in vitro provide tremendous advantages for using kinesin in engineering application. Moreover, kinesin's ability to utilize chemical energy from their ambient environment simplifies microdevice design and eliminates the requirement of large external power supplies. Here, I present three devices into which kinesin motors are integrated. Two of the devices efficiently rectify the mechanical power produced by kinesins into designated directions. The third device leverages techniques of rectifying kinesin's power to achieve highly sensitive bio-molecule sorting. These devices demonstrate that kinesin-powered devices are practical and have significant potential for future applications.To enhance future technological application, it is important to understand the molecular mechanisms of kinesin. Kinesin has been intensively studied for decades however, one major gap relates to the mechanism(s) that control the direction of kinesin motors. Here, I used mutagenesis to investigate which structural domains determine the directionality of conventional kinesin and Ncd, the most frequently used models for directionality studies. The result suggests that structural components that control kinesins' directionality are also involved generating motor's motility. Therefore, it is challenging to alter kinesins' directionality and simultaneously keeping their motility intact. My data shows that both kinesin and Ncd use components close to their head domains for controlling their directionality: they are neck-linker and C-terminal neck domain for kinesin and Ncd, respectively.An important physiological property of conventional kinesin is to take a large number of steps along the microtubule. This processive motion is believed to be based on a strain-coordinated, alternate catalysis. Little work has directly investigated the intra-molecular strain coordination of kinesin's movement. To test this intra-molecular strain hypothesis I inserted a set of flexible residues at the junction between kinesin's neck domain and neck-linker. The single motor gliding assays show that the wild-type and mutated kinesins move with the same velocity, but the run lengths of mutants decrease. These biophysical properties of these kinesin mutants suggest that kinesins may use different mechanism(s) other than the mechanical strain to coordinate their processive movement.