The alpha subunit of sea urchin sperm outer arm dynein mediates structural and rigor binding to microtubules.
The alpha subunit of sea urchin sperm outer arm dynein mediates structural and rigor binding to microtubules.
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DOI：
10.1083/jcb.118.5.1189
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发表时间：
1992-09
影响因子：
7.8
通讯作者：
Witman, G B
中科院分区：
文献类型：
--
作者：
Moss, A G;Sale, W S;Fox, L A;Witman, G B
玻璃吸附的完整海胆外臂动力蛋白及其β/IC 1亚基支持微管的运动，但在ATP耗尽时不会形成僵硬复合物（16）。我们在这里表明，严谨性是一个功能的孤立的完整的外臂，这种属性细分与其α重链。完整的动力蛋白介导ATP敏感性微管束的形成，纯化的α重链也是如此，这表明两种颗粒都能够以ATP敏感的方式与微管结合。相比之下，β/IC 1亚基不捆绑微管。与完整的动力蛋白形成的束由平行微管的带状片组成，所述平行微管由54 nm（中心到中心）分开，并显示与原位外部双峰相同的动力蛋白臂的纵向重复（24 nm）和横截面几何形状。由α重链形成的束由中心间距为43 nm的微管组成，并显示罕见的精细横桥。与由完整臂形成的桥相反，由α亚基形成的连接是不规则间隔的，表明α重链与微管的结合是不合作的。共沉淀研究表明：（a）一些完整的动力蛋白以ATP依赖性方式结合，一些以ATP非依赖性方式结合;（B）β/IC 1亚基在任何条件下都不与微管共沉淀;（c）α重链在不存在或存在MgATP 2-的情况下与微管共沉淀。这些结果表明，在完整臂中观察到的结构结合也是其α重链的特性。我们的结论是，而力的产生是一个功能的β/IC 1亚基，结构和ATP敏感性（僵硬）结合的手臂微管介导的α亚基。
Glass-adsorbed intact sea urchin outer arm dynein and its beta/IC1 subunit supports movement of microtubules, yet does not form a rigor complex upon depletion of ATP (16). We show here that rigor is a feature of the isolated intact outer arm, and that this property subfractionates with its alpha heavy chain. Intact dynein mediates the formation of ATP-sensitive microtubule bundles, as does the purified alpha heavy chain, indicating that both particles are capable of binding to microtubules in an ATP-sensitive manner. In contrast, the beta/IC1 subunit does not bundle microtubules. Bundles formed with intact dynein are composed of ribbon-like sheets of parallel microtubules that are separated by 54 nm (center-to-center) and display the same longitudinal repeat (24 nm) and cross-sectional geometry of dynein arms as do outer doublets in situ. Bundles formed by the alpha heavy chain are composed of microtubules with a center-to-center spacing of 43 nm and display infrequent, fine crossbridges. In contrast to the bridges formed by the intact arm, the links formed by the alpha subunit are irregularly spaced, suggesting that binding of the alpha heavy chain to the microtubules is not cooperative. Cosedimentation studies showed that: (a) some of the intact dynein binds in an ATP- dependent manner and some binds in an ATP-independent manner; (b) the beta/IC1 subunit does not cosediment with microtubules under any conditions; and (c) the alpha heavy chain cosediments with microtubules in the absence or presence of MgATP2-. These results suggest that the structural binding observed in the intact arm also is a property of its alpha heavy chain. We conclude that whereas force-generation is a function of the beta/IC1 subunit, both structural and ATP-sensitive (rigor) binding of the arm to the microtubule are mediated by the alpha subunit.