Department of Biological Physics, Eötvös University, Budapest, Hungary.
Biophys J. 2011 Apr 6;100(7):1729-36. doi: 10.1016/j.bpj.2011.01.039.
Conventional kinesin is a two-headed homodimeric motor protein, which is able to walk along microtubules processively by hydrolyzing ATP. Its neck linkers, which connect the two motor domains and can undergo a docking/undocking transition, are widely believed to play the key role in the coordination of the chemical cycles of the two motor domains and, consequently, in force production and directional stepping. Although many experiments, often complemented with partial kinetic modeling of specific pathways, support this idea, the ultimate test of the viability of this hypothesis requires the construction of a complete kinetic model. Considering the two neck linkers as entropic springs that are allowed to dock to their head domains, and incorporating only the few most relevant kinetic and structural properties of the individual heads, we develop here the first, to our knowledge, detailed, thermodynamically consistent model of kinesin that can 1), explain the cooperation of the heads (including their gating mechanisms) during walking, and 2), reproduce much of the available experimental data (speed, dwell-time distribution, randomness, processivity, hydrolysis rate, etc.) under a wide range of conditions (nucleotide concentrations, loading force, neck-linker length and composition, etc.). Besides revealing the mechanism by which kinesin operates, our model also makes it possible to look into the experimentally inaccessible details of the mechanochemical cycle and predict how certain changes in the protein affect its motion.
传统的驱动蛋白是一种具有两个头部的同二聚体马达蛋白，它能够通过水解 ATP 沿着微管进行连续运动。其连接两个马达结构域的颈环，能够经历对接/脱接的转变，被广泛认为在两个马达结构域的化学循环协调中起着关键作用，进而在力的产生和定向运动中发挥作用。尽管许多实验，通常辅以特定途径的部分动力学建模，支持了这一观点，但对这一假设的可行性进行最终检验需要构建一个完整的动力学模型。考虑到两个颈环作为允许对接其头部结构域的熵弹簧，并仅包含各个头部的几个最相关的动力学和结构特性，我们在这里开发了第一个，据我们所知，详细的、热力学一致的驱动蛋白模型，该模型能够 1）解释头部在运动过程中的协同作用（包括它们的门控机制），以及 2）在广泛的条件下（核苷酸浓度、加载力、颈环长度和组成等）再现大部分可用的实验数据（速度、停留时间分布、随机性、连续性、水解率等）。除了揭示驱动蛋白的工作机制外，我们的模型还可以深入了解机械化学循环中实验无法触及的细节，并预测蛋白质的某些变化如何影响其运动。
