Average velocity
The average velocity reported for microtubules propelled by kinesin expressed in insect systems is much higher than that reported for kinesin expressed in E. coli with a calculated mean and median of approximately 2.9330μm/s and 2.7974μm/s respectively for kinesin expressed in insect systems and 1.1579μm/s and 1.0903μm/s respectively for kinesin expressed in E. coli. This result is similar to result obtained by Korten et al. (15: 64) and Agayan et al. (29: 2265–2272) and the lower velocity observed in microtubules propelled by kinesin expressed in E. coli is likely due to the presence of immobile kinesins of a which it has been discovered that a few of these motor proteins malfunctioning can eventually degrade the whole transport system (Nam and Epureanu 1: 14).
Average diffusion
Average diffusion in microtubules propelled by kinesin expressed in insects with mean and median of approximately 0.4414μm2/s and 0.4737μm2/s respectively exceeds that of E. coli with mean and median of approximately 0.0839μm2/s and 0.0851μm2/s respectively. Although the factors affecting diffusion in kinesin has not been fully understood, Ken’ya et al. (283: 36465–36473) in their research on Yeast Kinesin-14 suggest that thermal forces can cause kinesin to diffuse along microtubules if the interactions between them and the microtubule is moderate enough such as to prevent sticking to the microtubules as well as dissociation from it. They further postulate that larger diffusion coefficient can result from weak, nonspecific interactions between microtubules and the N-terminal domain of kinesin, permitting repeated binding to microtubules. Furthermore, research has pointed out that over long distances, diffusional recycling of kinesin is not effective (Kholodenko 206: 2073–2082; Miller and Heidemann 314: 1981–1990; Popov and Poo 12: 77–85; Sabry 14: 1247–1256).
Suggestion for further study
The fate of kinesins post cargo delivery has not yet been fully understood with several scientists suggesting that degradation of these motor proteins occur at the nerve terminals, others that they are recycled through retrograde motors and yet others that recycling of these motor proteins occurs through diffusion (Blasius et al. 8: 1). Although various works carried out by researchers such as Blasius et al. (8: 1 - 11) point out that kinesin-1 motors are recycled through diffusion for several rounds of transport, more still needs to be done to completely unravel the fate of these motors after transport completion.
Works Cited
Agayan, R.R., Tucker, R., Nitta, T., Ruhnow, F., Walter, W. J., Diez, S. and Hess, H. “Optimization of Isopolar Microtubule Arrays.” Langmuir 29.7 (2013): 2265–2272. Web. 24 July. 2016.
Blasius, T.L., Reed, N., Slepchenko, B.M. and Verhey, K.J. “Recycling of Kinesin-1 Motors by Diffusion after Transport”. PLoS ONE 8.9 (2013): 1 – 11. Web. 2 August. 2016.
Furuta, Ken’ya et al. “Diffusion and Directed Movement: In Vitro Motile Properties of Fission Yeast Kinesin-14 Pkl1.” The Journal of Biological Chemistry 283.52 (2008): 36465–36473. Web. 3 August. 2016.
Kholodenko, B.N. “Four-Dimensional Organization of Protein Kinase Signalling Cascades: The Roles of Diffusion, Endocytosis and Molecular Motors. J Exp Biol 206 (2003): 2073–2082. Web. 3 August. 2016.
Korten, T., Chaudhuri, S., Tavkin, E., Braun, M. and Diez, S. “Kinesin-1 Expressed in Insect Cells Improves Microtubule in Vitro Gliding Performance, Long-Term Stability and Guiding Efficiency in Nanostructures. IEEE Transactions on Nanobioscience 15.1 (2016): 62-69. Web. 24 July. 2016.
Kurland, C. and Gallant, J. “Errors of Heterologous Protein Expression” Curr. Opin. Biotechnol. 7.5 (1996): 489 – 493. Web. 31 July. 2016.
Miller, K.E. and Heidemann, S.R. “What is Slow Axonal Transport?” Exp Cell Res 314 (2008): 1981–1990. Web. 3 August. 2016.
Nam, W. and Epureanu, B.I. “Effects of Obstacles on the Dynamics of Kinesins, Including Velocity and Run Length, Predicted by a Model of Two Dimensional Motion.” PLoS ONE 11.1 (2016): 1 – 18. Web. 2 August. 2016.
Popov, S. and Poo, M.M. “Diffusional Transport of Macromolecules in Developing Nerve Processes. J Neurosci 12 (1992): 77 – 85. Web. 3. August. 2016.
Sabry, J., O’Connor, T.P. and Kirschner, M.W. “Axonal Transport of Tubulin in Ti1 Pioneer Neurons in situ. Neuron 14 (1995): 1247 – 1256. Web. 3 August. 2016.
Scharrel, L., Ma, R., Schneider, R., Jülicher, F. and Diez, S. “Multimotor Transport in a System of Active and Inactive Kinesin-1 Motors,” Biophys. J. 107.2 (2014): 365 – 372. Web. 24 July. 2016.
