Heterogeneity in kinesin function

Abstract

The kinesin family proteins are often studied as prototypical molecular motors; a deeper understanding of them can illuminate regulation of intracellular transport. It is typically assumed that they function identically. Here we find that this assumption of homogeneous function appears incorrect: variation among motors' velocities in vivo and in vitro is larger than the stochastic variation expected for an ensemble of "identical" motors. When moving on microtubules, slow and fast motors are persistently slow, and fast, respectively. We develop theory that provides quantitative criteria to determine whether the observed single-molecule variation is too large to be generated from an ensemble of identical molecules. To analyze such heterogeneity, we group traces into homogeneous sub-ensembles. Motility studies varying the temperature, pH and glycerol concentration suggest at least 2 distinct functional states that are independently affected by external conditions. We end by investigating the functional ramifications of such heterogeneity through Monte-Carlo multi-motor simulations.

A 6-nm ultra-photostable DNA FluoroCube for fluorescence imaging

“…2 c ). Previous work demonstrated that different kinesins can have different velocities 23 , but our prolonged observations showed that even individual kinesins undergo considerable velocity fluctuations over time.…”

A 6-nm ultra-photostable DNA Fluorocube for fluorescence imaging

“…2 c ). Previous work demonstrated that different kinesins can have different velocities 21 , but our prolonged observations showed that even individual kinesins undergo considerable velocity fluctuations over time.…”

A fluid membrane enhances the velocity of cargo transport by small teams of kinesin-1

“…Heterogeneity in single-kinesin velocity has been previously observed for the same motor construct. 46,47 Here, we found that the fraction of slow runs increased substantially as the density of motors on the cargo increased. For example, at a motile fraction of 0.8, 56% of cargos moved slower than 0.6 µm/s [ Fig.…”

“…The velocity of a single motor is not typically uniform within a population of kinesins. 46,47 During transport by a small team of kinesins, the faster motors lead the cargo and the slower motors lag behind; forcebased interactions between motors tend to prompt the lagging kinesin to dissociate prematurely from the microtubule, 6 causing the cargo to tumble forward to the position of the leading motor. Sliding of motors within the lipid membrane delays force-based interactions between motors and enables the leading kinesin to move forward further before the lagging motor dissociates.…”