Abstract
Kinesin-1 is a motor protein that can step processively on microtubule by hydrolyzing ATP molecules, playing an essential role in intracellular transports. To better understand the mechanochemical coupling of the motor stepping cycle, numerous structural, biochemical, single molecule, theoretical modeling and numerical simulation studies have been undertaken for the kinesin-1 motor. Recently, a novel ultraresolution optical trapping method was employed to study the mechanics of the kinesin-1 motor and new results were supplemented to its stepping dynamics. In this commentary, the new single molecule results are explained well theoretically with one of the models presented in the literature for the mechanochemical coupling of the kinesin-1 motor. With the model, various prior experimental results for dynamics of different families of N-terminal kinesin motors have also been explained quantitatively.
Highlights
Kinesin-1 molecular motor is the firstly discovered member of kinesin superfamily that can be classified into 14 subfamilies and an ungrouped subfamily called orphan kinesins [1,2]
Kinesin-1 has been studied thoroughly and can be regarded as the model system to study the mechanism of the mechanochemical coupling of the kinesin superfamily
Kinesin-1 can step processively on microtubules (MTs) by hydrolyzing ATP molecules, which is responsible for cargo transports in cells
Summary
Kinesin-1 molecular motor is the firstly discovered member of kinesin superfamily that can be classified into 14 subfamilies and an ungrouped subfamily called orphan kinesins [1,2]. Sudhakar et al [23] developed germanium nanospheres with diameter of about 70 nm as optical trapping probes to study the stepping dynamics of truncated rat kinesin-1 motor, which enhances greatly the spatiotemporal resolution that is limited by using traditional micrometer-sized spheres They found that each 8-nm mechanical step consists of two 4-nm substeps, with the dwell time for the second substep being much shorter than that for the first one. Instead of dissociation from MT, the slip of the motor on MT was observed under high backward loads, which occurs always during the dwell period before the second substep In this commentary, these new single molecule results measured by Sudhakar et al [23] are explained well by the theoretical analysis based on one of the models presented in the literature for the mechanochemical coupling of kinesin-1 motors [24]. As shown before [18,24,25,26,27,28,29,30], this model can explain quantitatively diverse experimental results about the load dependency of the stepping dynamics for various families of N-terminal kinesin motors
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