Direct visualization of human myosin II force generation using DNA origami-based thick filaments
Direct visualization of human myosin II force generation using DNA origami-based thick filaments
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DOI：
10.1038/s42003-019-0683-0
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发表时间：
2019-11-27
影响因子：
5.9
通讯作者：
Iwaki, Mitsuhiro
中科院分区：
文献类型：
--
作者：
Fujita, Keisuke;Ohmachi, Masashi;Iwaki, Mitsuhiro
肌节是肌肉的最小机械单位，由肌球蛋白组成，肌球蛋白自组装成粗丝，粗丝与肌动蛋白为基础的细丝相互作用，形成高度结构化的晶格。这种复合物对肌球蛋白产生力施加了几何限制。然而，单个肌球蛋白如何在限制内产生力仍然是难以捉摸的，并且传统的合成细丝不能概括肌节中的对称双极细丝。在这里，我们使用DNA折纸设计了粗丝，其中包含人类肌肉肌球蛋白，以直接可视化在有限空间中产生力时头部的运动。我们发现，当头部扩散时，它与肌动蛋白丝弱相互作用，然后强烈结合优先向前区域作为布朗棘轮。在强有力的约束下，两步摆臂主要停在第一步，偶尔反向。我们的研究结果说明了我们的DNA折纸为基础的分析系统的有用性，以解剖马达蛋白的机械细节。
The sarcomere, the minimal mechanical unit of muscle, is composed of myosins, which self-assemble into thick filaments that interact with actin-based thin filaments in a highly-structured lattice. This complex imposes a geometric restriction on myosin in force generation. However, how single myosins generate force within the restriction remains elusive and conventional synthetic filaments do not recapitulate the symmetric bipolar filaments in sarcomeres. Here we engineered thick filaments using DNA origami that incorporate human muscle myosin to directly visualize the motion of the heads during force generation in a restricted space. We found that when the head diffuses, it weakly interacts with actin filaments and then strongly binds preferentially to the forward region as a Brownian ratchet. Upon strong binding, the two-step lever-arm swing dominantly halts at the first step and occasionally reverses direction. Our results illustrate the usefulness of our DNA origami-based assay system to dissect the mechanistic details of motor proteins.