The Mechanism Of Bio-molecular Motor Kinesin

Conventional kinesin is a homodimeric motor protein that transports molecular cargos along filamentous microtubule by hydrolyzing ATP molecules. As compared to other cytoskeleton-based Intracellular transporters, conventional kinesin is superior in processivity, unidirectionality and load-resisting capacity, and thus has been heatedly studied.This article develops a comprehensive physical model of conventional kinesin on the basis of a rather unique free-energy analysis. This study reveals the unified mechanisms of the motor's forward walking, stall state and backward walking for a broad range of loads. This study shows quantitatively how this intrinsic mechanism causes kinesin's superior performance for intracellular transportation. Besides, some present controversies on the frontier of kinesin studies have been solved. For instance: 1. The relationship between the consecutive forward walking capacity and ATP concentrations. 2. The relationship between stall force and ATP concentrations. 3. The relationship between consecutive backward walking and ATP concentrations.This study quantitatively proves that, conventional kinesin is an evolutionarily fine-tuned molecular ratchet-and-pawl device. The ratchet mechanism guarantees the motor protein's sturdy unidirectionality, while the pawl mechanism ensures the motor protein's forward walking efficiency. A buffer regime protects the motor from large fluctuation of loads during the walking in the crowded interior of the cell. However, if the load is too large or lasts too long, the motor protein automatically breaks away from the track, and thus avoids wasting too much resource (ATP molecules). The unambiguous physical understanding developed in this thesis of these amazing characteristics of kinesin will be a valuable reference to future development of high-performance artificial molecular motors.