Kinesin-driven sorting machine on large-scale microtubule arrays

Kinesin molecules can be regarded as engines (linear motors) that utilize the chemical energy of the biofuel adenosine triphosphate (ATP) to move in nanometer-precise steps along proteinaceous microtubule rails. In cell-free environments, cargoes made from different materials, including gold, silicon, glass, carbon, and polystyrene were shown to be transported by the kinesin motor along microtubules. In a previous paper, we demonstrated that the directional control of this transport can be realized using arrays of parallel and isopolar microtubules; prepared by a flow field technique. The presented paper describes conditions to achieve a continuous transport of kinesin-loaded cargoes over hundreds of micrometers. These conditions include the usage of arrays in which the microtubules were immobilized at densities which make sure that the maximal lateral and longitudinal distances do not exceed the dimensions of the cargo. Additionally, each cargo to be transported had to be loaded with significantly more than one kinesin molecule. Basing on the application of laser tweezers, an approach is presented by which kinesin-driven cargoes can be transferred from one microtubule rail to a preselected other one. Corresponding to the orientation of the new rail, specified cargoes can be delivered to a predefined destination. The combination of laser trapping technologies with kinesin-driven cargo transport on highly ordered microtubule arrays might contribute to construct motor protein-based devices able to sort particles as well as single molecules.