ANALYSIS OF CHANGES IN THE GLIDING DIRECTION OF KINESIN-DRIVEN MICROTUBULES FOCUSING ON THEIR LENGTH AND KINESIN DENSITY

Kinesins, motor proteins moving along microtubules (MTs) in cells, can potentially be utilized as nano-scale transport systems with an inverted gliding assay, in which the MTs glide on a kinesin-coated surface. Although the key requirements include controls of the gliding direction of MTs, the details of motility properties of gliding MTs have not been elucidated. Here, the angular velocity of gliding MTs was quantitatively measured, particularly focusing on the effects of MT length and kinesin density. The gliding assay of MTs was performed on a substrate coated with kinesin densities of 7.5, 38, and 75 µg/ml that resulted in kinesin spacing of 7.8, 4.2, and 3.1 µm, respectively. The angular velocity for MTs shorter than kinesin spacing significantly decreased with increasing length, and that for MTs longer than kinesin spacing was not affected by their length. Moreover, the angular velocity for MTs longer than kinesin spacing was substantially higher at lower kinesin density. These results suggest that both the number of kinesins associated with MTs and the kinesin spacings may determine the gliding direction.