Oriola David, Casademunt Jaume
Departament d'Estructura i Constituents de la Matèria, Facultat de Física, Universitat de Barcelona, Avinguda Diagonal 647, E-08028 Barcelona, Spain.
Phys Rev E Stat Nonlin Soft Matter Phys. 2014 Mar;89(3):032722. doi: 10.1103/PhysRevE.89.032722. Epub 2014 Mar 31.
We study in detail the cooperative action of small groups of KIF1A motors in its monomeric (single-headed) form within an arrangement relevant to vesicle traffic or membrane tube extraction. It has been recently shown that under these circumstances, the presence of a finite dwell time in the motor cycle contributes to remarkably enhance collective force generation [D. Oriola and J. Casademunt, Phys. Rev. Lett. 111, 048103 (2013)]. We analyze this mechanism in detail by means of a two-state noise-driven ratchet model with hard-core repulsive interactions. We obtain staircase-shaped velocity-force curves and show that motors self-organize in clusters with a nontrivial force distribution that conveys a large part of the load to the central motors. Under heavy loads, large clusters adopt a synchronic mode of totally asymmetric steps. We also find a dramatic increase of the collective efficiency with the number of motors. Finally, we complete the study by addressing different interactions that impose spatial constraints such as rigid coupling and raft-induced confinement. Our results reinforce the hypothesis that the specificity of KIF1A to axonal vesicular transport may be deeply related to its high cooperativity.
我们详细研究了呈单体（单头）形式的小群KIF1A马达在与囊泡运输或膜管提取相关的一种排列中的协同作用。最近研究表明，在这些情况下，马达循环中有限停留时间的存在有助于显著增强集体力的产生[D. 奥里奥拉和J. 卡萨德蒙特，《物理评论快报》111, 048103 (2013)]。我们通过一个具有硬核排斥相互作用的两态噪声驱动棘轮模型详细分析了这一机制。我们得到了阶梯状的速度 - 力曲线，并表明马达自组织成具有非平凡力分布的簇，该分布将大部分负载传递给中央马达。在重负载下，大的簇采用完全不对称步的同步模式。我们还发现集体效率随着马达数量急剧增加。最后，我们通过研究施加空间约束的不同相互作用（如刚性耦合和筏诱导限制）完成了这项研究。我们的结果强化了这样一种假设，即KIF1A对轴突囊泡运输的特异性可能与其高协同性密切相关。
