The kinetic mechanism of myosin V
The kinetic mechanism of myosin V
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DOI：
10.1073/pnas.96.24.13726
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发表时间：
1999-11-23
影响因子：
11.1
通讯作者：
Sweeney, HL
中科院分区：
文献类型：
--
作者：
De La Cruz, EM;Wells, AL;Sweeney, HL
肌球蛋白V是一种非传统的肌球蛋白，被认为能在肌动蛋白丝上持续移动，类似于驱动蛋白在微管上的移动[梅塔，A.D.等人（1999年）《自然》（伦敦）400卷，590 - 593页]。为了确定肌球蛋白V允许其持续移动的独特性质，我们对肌球蛋白V马达进行了详细的动力学分析。我们表达了一种截短的单头肌球蛋白V构建体，它结合单个轻链以研究其固有动力学，不受分子其他区域施加的限制。数据表明，与之前所描述的任何肌球蛋白不同，在ATP存在的情况下，单头肌球蛋白V在其动力学循环的大部分时间（>70%）都与肌动蛋白紧密结合。这种动力学调节是通过提高在与肌动蛋白紧密结合之前的几个速率，并通过减慢ADP释放速率同时延长紧密结合状态的持续时间来实现的。最终结果是产生了一种与之前所描述的任何肌球蛋白都不同的肌球蛋白，即ADP释放是肌动蛋白激活的ATP酶循环的限速步骤。因此，由于多种动力学适应性变化，肌球蛋白V被调整为能在肌动蛋白上持续移动，并且能够在比任何其他已描述的肌球蛋白更低的马达密度下运输货物。
Myosin V is an unconventional myosin proposed to he processive on actin filaments, analogous to kinesin on a microtubule [Mehta, A. D., ef al. (1999) Nature (London) 400, 590-593]. To ascertain the unique properties of myosin V that permit processivity, we undertook a detailed kinetic analysis of the myosin V motor. We expressed a truncated, single-headed myosin V construct that bound a single light chain to study its innate kinetics, free from constraints imposed by other regions of the molecule. The data demonstrate that unlike any previously characterized myosin a single-headed myosin V spends most of its kinetic cycle (>70%) strongly bound to actin in the presence of ATP. This kinetic tuning is accomplished by increasing several of the rates preceding strong binding to actin and concomitantly prolonging the duration of the strongly bound state by slowing the rate of ADP release. The net result is a myosin unlike any previously characterized, in that ADP release is the rate-limiting step for the actin-activated ATPase cycle. Thus, because of a number of kinetic adaptations, myosin V is tuned for processive movement on actin and will be capable of transporting cargo at lower motor densities than any other characterized myosin.