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摘要翻译：
在构成动蛋白机械力化学循环的多个步骤中，最有趣的事件之一是动蛋白从一个微管结合位点向另一个微管结合位点移动8nm步。然而，在较短的时间尺度(～100微秒）内发生的步进运动超出了现有实验的分辨率，因此对8nm步进内的实时动力学仍缺乏基本的理解。例如，导致颈部连接器未对接到对接过渡的动力冲程（或构象变化）的速率尚不清楚，而在8nm步骤中是否存在子步骤在驱动蛋白社区仍是一个有争议的问题。利用驱动蛋白二聚体和由13条原丝组成的MT的显式结构，我们研究了不同功率行程率(kp)下的步进动力学。我们估计1/kp<~20微秒，以避免平均时间轨迹中的子步。对于1/kp>20微秒的慢功率冲程，平均时间轨迹显示了一个子步骤，暗示了瞬态中间体的存在，这让人想起最近在高分辨率下进行的单分子实验。我们确定中间体是一种构象，其中栓系头部被困在邻近PF的侧向结合位点。我们还发现，在驱动蛋白与MT结合之前，在过渡态系综上的结合基序部分展开（裂解）。
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英文标题：
《Mechanical control of the directional stepping dynamics of the kinesin
motor》
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作者：
Changbong Hyeon and Jos\'e N. Onuchic
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最新提交年份：
2007
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分类信息：
一级分类：Physics 物理学
二级分类：Soft Condensed Matter 软凝聚态物质
分类描述：Membranes, polymers, liquid crystals, glasses, colloids, granular matter
膜，聚合物，液晶，玻璃，胶体，颗粒物质
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一级分类：Physics 物理学
二级分类：Statistical Mechanics 统计力学
分类描述：Phase transitions, thermodynamics, field theory, non-equilibrium phenomena, renormalization group and scaling, integrable models, turbulence
相变，热力学，场论，非平衡现象，重整化群和标度，可积模型，湍流
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一级分类：Quantitative Biology 数量生物学
二级分类：Biomolecules 生物分子
分类描述：DNA, RNA, proteins, lipids, etc.; molecular structures and folding kinetics; molecular interactions; single-molecule manipulation.
DNA、RNA、蛋白质、脂类等；分子结构与折叠动力学；分子相互作用；单分子操作。
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英文摘要：
Among the multiple steps constituting the kinesin's mechanochemical cycle, one of the most interesting events is observed when kinesins move an 8-nm step from one microtubule (MT)-binding site to another. The stepping motion that occurs within a relatively short time scale (~100 microsec) is, however, beyond the resolution of current experiments, therefore a basic understanding to the real-time dynamics within the 8-nm step is still lacking. For instance, the rate of power stroke (or conformational change), that leads to the undocked-to-docked transition of neck-linker, is not known, and the existence of a substep during the 8-nm step still remains a controversial issue in the kinesin community. By using explicit structures of the kinesin dimer and the MT consisting of 13 protofilaments (PFs), we study the stepping dynamics with varying rates of power stroke (kp). We estimate that 1/kp <~ 20 microsec to avoid a substep in an averaged time trace. For a slow power stroke with 1/kp>20 microsec, the averaged time trace shows a substep that implies the existence of a transient intermediate, which is reminiscent of a recent single molecule experiment at high resolution. We identify the intermediate as a conformation in which the tethered head is trapped in the sideway binding site of the neighboring PF. We also find a partial unfolding (cracking) of the binding motifs occurring at the transition state ensemble along the pathways prior to binding between the kinesin and MT.
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PDF链接：
https://arxiv.org/pdf/710.4558
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