Small teams of myosin Vc motors coordinate their stepping for efficient cargo transport on actin bundles
Small teams of myosin Vc motors coordinate their stepping for efficient cargo transport on actin bundles
复制标题
DOI：
10.1074/jbc.m117.780791
复制
发表时间：
2017-06-30
影响因子：
4.8
通讯作者：
Ali, M. Yusuf
中科院分区：
文献类型：
--
作者：
Krementsova, Elena B.;Furuta, Ken'ya;Ali, M. Yusuf
肌凝蛋白Vc （myoVc）在脊椎动物V类肌凝蛋白异构体中是独特的，因为它需要马达组在单个肌动蛋白细丝上连续移动。myoVc的单分子不能在不解离的情况下从一个肌动蛋白结合位点到下一个肌动蛋白结合位点进行多次交替的步骤，这与已被充分研究的肌凝蛋白Va （myoVa）异构体形成鲜明对比。在低盐条件下，单个myoVc马达可以在肌动蛋白束上运动，而在生理离子强度下，即使是成群的myoVc马达也需要肌动蛋白束来维持连续运动。在这里，我们将定义数量的myoVc或myoVa分子连接到DNA纳米结构作为合成货物。利用全内反射荧光显微镜，我们比较了myoVc与myoVa群的步进行为，以及myoVc在单个肌动蛋白细丝和肌动蛋白束上的步进模式。与肌动蛋白丝相比，myoVc和myoVa组的运动长度随运动细胞数量的增加而增加，但只有多个myoVc运动细胞在肌动蛋白束上的运动长度增加。通过将量子点绑定到电机域来解决单个myoVc电机的步进行为，我们发现两个myoVc电机的耦合显着减少了单个myoVc电机经常观察到的无用的后退和侧步。两个耦合myoVc电机之间电机间距离的变化影响步进动力学，表明机械张力协调了两个myoVc电机的步进行为，以实现有效的定向运动。我们的研究提供了一个分子基础来解释myoVc马达团队是如何适合于运输诸如肌动蛋白束上的酶原颗粒之类的货物。
Myosin Vc (myoVc) is unique among vertebrate class V myosin isoforms in that it requires teams of motors to move continuously on single actin filaments. Single molecules of myoVc cannot take multiple hand-over-hand steps from one actin-binding site to the next without dissociating, in stark contrast to the well studied myosin Va (myoVa) isoform. At low salt, single myoVc motors can, however, move processively on actin bundles, and at physiologic ionic strength, even teams of myoVc motors require actin bundles to sustain continuous motion. Here, we linked defined numbers of myoVc or myoVa molecules to DNA nanostructures as synthetic cargos. Using total internal reflectance fluorescence microscopy, we compared the stepping behavior of myoVc versus myoVa ensembles and myoVc stepping patterns on single actin filaments versus actin bundles. Run lengths of both myoVc and myoVa teams increased with motor number, but only multiple myoVc motors showed a run-length enhancement on actin bundles compared with actin filaments. By resolving the stepping behavior of individual myoVc motors with a quantum dot bound to the motor domain, we found that coupling of two myoVc motors significantly decreased the futile back and side steps that were frequently observed for single myoVc motors. Changes in the inter-motor distance between two coupled myoVc motors affected stepping dynamics, suggesting that mechanical tension coordinates the stepping behavior of two myoVc motors for efficient directional motion. Our study provides a molecular basis to explain how teams of myoVc motors are suited to transport cargos such as zymogen granules on actin bundles.