The maintenance of intracellular processes, like organelle transport and cell division, depend on bidirectional movement along microtubules. These processes typically require kinesin and dynein motor proteins, which move with opposite directionality. Because both types of motors are often simultaneously bound to the cargo, regulatory mechanisms are required to ensure controlled directional transport. Recently, it has been shown that parameters like mechanical motor activation, ATP concentration and roadblocks on the microtubule surface differentially influence the activity of kinesin and dynein motors in distinct manners. However, how these parameters affect bidirectional transport systems has not been studied. Here, we investigate the regulatory influence of these three parameters using in vitro gliding motility assays and stochastic simulations. We find that the number of active kinesin and dynein motors determines the transport direction and velocity, but that variations in ATP concentration and roadblock density have no significant effect. Thus, factors influencing the force balance between opposite motors appear to be important, whereas the detailed stepping kinetics and bypassing capabilities of the motors only have a small effect.

细胞内过程的维持，如细胞器运输和细胞分裂，取决于沿微管的双向运动。这些过程通常需要驱动蛋白和动力蛋白，它们的运动方向相反。由于两种类型的电动机通常同时绑定到货物，因此需要使用调节机制来确保可控制的定向运输。最近，已经显示出参数如机械马达激活，ATP浓度和微管表面上的障碍物以不同的方式差异地影响驱动蛋白和动力蛋白马达的活性。但是，尚未研究这些参数如何影响双向运输系统。在这里，我们使用体外研究这三个参数的调节作用滑行运动分析和随机模拟。我们发现，主动驱动蛋白和动力蛋白的数量决定了运输方向和速度，但是ATP浓度和路障密度的变化没有明显影响。因此，影响相对电动机之间力平衡的因素似乎很重要，而电动机的详细步进动力学和旁路能力仅产生很小的影响。