Theory and Bio-Systems, Max Planck Institute of Colloids and Interfaces, Science Park Golm, 14424, Potsdam, Germany.
Sci Rep. 2019 Jan 24;9(1):454. doi: 10.1038/s41598-018-37126-0.
Many active cellular processes such as long-distance cargo transport, spindle organization, as well as flagellar and ciliary beating are driven by molecular motors. These motor proteins act collectively and typically work in small teams. One particularly interesting example is two teams of antagonistic motors that pull a common cargo into opposite directions, thereby generating mutual interaction forces. Important issues regarding such multiple motor systems are whether or not motors from the same team share their load equally, and how the collectively generated forces depend on the single motor properties. Here we address these questions by introducing a stochastic model for cargo transport by an arbitrary number of elastically coupled molecular motors. We determine the state space of this motor system and show that this space has a rather complex and nested structure, consisting of multiple activity states and a large number of elastic substates, even for the relatively small system of two identical motors working against one antagonistic motor. We focus on this latter case because it represents the simplest tug-of-war that involves force sharing between motors from the same team. We show that the most likely motor configuration is characterized by equal force sharing between identical motors and that the most likely separation of these motors corresponds to a single motor step. These likelihoods apply to different types of motors and to different elastic force potentials acting between the motors. Furthermore, these features are observed both in the steady state and during the initial build-up of elastic strains. The latter build-up is non-monotonic and exhibits a maximum at intermediate times, a striking consequence of mutual unbinding of the elastically coupled motors. Mutual strain-induced unbinding also reduces the magnitude of the collectively generated forces. Our computational approach is quite general and can be extended to other motor systems such as motor teams working against an optical trap or mixed teams of motors with different single motor properties.
许多活跃的细胞过程，如长途货物运输、纺锤体组织以及鞭毛和纤毛的拍打，都是由分子马达驱动的。这些马达蛋白集体作用，通常以小团队的形式工作。一个特别有趣的例子是两个对抗性马达团队，它们将一个共同的货物拉向相反的方向，从而产生相互作用的力。关于这种多马达系统的重要问题是，来自同一团队的马达是否平等地分担它们的负载，以及集体产生的力如何取决于单个马达的特性。在这里，我们通过引入一个任意数量的弹性耦合分子马达货物运输的随机模型来解决这些问题。我们确定了这个马达系统的状态空间，并表明这个空间具有相当复杂和嵌套的结构，由多个活性状态和大量的弹性亚状态组成，即使对于两个相同的马达对抗一个拮抗马达的相对较小的系统也是如此。我们关注后一种情况，因为它代表了最简单的拔河比赛，涉及来自同一团队的马达之间的力共享。我们表明，最有可能的马达配置是相同马达之间的力平等共享的特征，并且这些马达最有可能的分离对应于单个马达步。这些可能性适用于不同类型的马达和作用在马达之间的不同弹性力势。此外，这些特征在稳态和弹性应变的初始建立期间都可以观察到。后者的建立是非单调的，并在中间时间表现出最大值，这是弹性耦合马达相互解联的显著后果。相互应变诱导的解联也降低了集体产生的力的大小。我们的计算方法非常通用，可以扩展到其他马达系统，例如对抗光学陷阱的马达团队或具有不同单个马达特性的混合马达团队。
