Characterization of Motility Properties of Kinesin-Driven Microtubules Towards Nano-Scale Transporter: Focusing on Length of Microtubules and Kinesin Density

Abstract

Kinesins, biomolecular motors 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 gliding direction and velocity of MTs, the details of motility properties of MTs have not been well known. In this study, we quantitatively measured angular and gliding velocities, particularly focusing on the effects of MT length and kinesin density. The gliding assay of MTs of up to 20 μm in length was performed on a substrate coated with the kinesin density of 7.5, 38, and 75 μg/ml that resulted in the kinesin spacing of 7.8, 4.2, and 3.1 μm, respectively. The angular velocity for MTs shorter than kinesin spacings significantly decreased with increasing their length, and that for MTs longer than kinesin spacings was not affected by their length. Moreover, the angular velocity was substantially higher at lower kinesin density. These results suggest that both the number of associated kinesins with MTs and the kinesin spacings may contribute to the gliding direction. In contrast, the gliding velocity was independent of the MT length, ranging from 0.3 to 0.5 μm/s with decreasing the kinesin density. This may potentially imply the existence of an underlying mechanism with respect to the number of kinesins per the unit length of MTs. Towards development of high throughput nano-scale transport systems, long MTs and low kinesin densities would be effective for high directionality and high velocity, respectively.