Allostery in myosins studied at the molecular level

描述（由申请人提供）：在典型的真核细胞的拥挤环境中，任何大于50 nm的物体实际上都是固定的，不能依靠扩散到达其目的地。因此，肌球蛋白马达进化为产生运输货物，细胞运动和细胞分裂的力量，这些过程对生命本身至关重要。这些马达在与肌动蛋白丝结合的同时，通过以受控的方式改变形状来转换化学自由能。所有马达蛋白的一个基本特征是它们的运动都是仔细协调的，因此马达通过特定的生化和机械状态耦合序列进行运动。这种协调的性质仍然不清楚，但它显然是必要的适当的运动功能。最近认识到，每个肌球蛋白类已经发展出特定的结构和动力学特征，允许跨肌球蛋白超家族的不同协调机制的比较。这些个体的适应性现在可以通过一系列先进的运动性测定来表征。这里提出的工作将确定变构协调机制，使用新的单分子操纵，以改变分子内的应变感受到的电机。通过机械地改变肌动蛋白丝的几何形状，将建立运动轨迹在传递应变中的作用。此外，通信机制将被确定为肌球蛋白V和肌球蛋白VI通过负载依赖性步进测量的条件下，两个头的电机是解耦的。这些机制将与肌球蛋白X，一个电机与不寻常的体内运动，这表明一种新形式的应变传感。这项研究的长期目标是揭示马达和马达系统是如何优化其细胞运输任务的。肌球蛋白运动性是各种正常和病理细胞功能所必需的，包括极化细胞结构的发育、细胞粘附和组织发育的形成、伤口愈合、细胞内运输和细胞分裂。这项研究将解决有关运动相关疾病背后的潜在生物学的关键问题，其中包括与感觉毛细胞中立体纤毛的适当发育和维持相关的几种形式的遗传性耳聋。

DESCRIPTION (provided by applicant): In the crowded environment of a typical eukaryotic cell, any object larger than 50 nm is effectively immobile and cannot rely on diffusion to arrive at its destination. As a result, myosin motors evolved to generate force for the transport of cargoes, cell motility, and cell division, processes that are critical for life itself. These motors convert chemical free energy by changing shape in a controlled manner while bound to actin filaments. A fundamental feature of all motor proteins is that their movements are carefully coordinated, so that the motor travels through a specific sequence of coupled biochemical and mechanical states. The nature of this coordination remains obscure, but it is clearly essential for proper motor function. The recent recognition that each myosin class has evolved specific structural and kinetic features allows for the comparison of different coordination mechanisms across the myosin super family. These individual adaptations may now be characterized by a host of advanced motility assays. The work proposed here will determine the allosteric coordination mechanisms using new single-molecule manipulations to alter the intramolecular strain felt by the motor. The role of the motor track in transmitting strain will be established, by mechanically altering the actin filament geometry. In addition, communication mechanisms will be identified for myosin V and myosin VI through load dependent stepping measurements under conditions where the two heads of the motor are uncoupled. These mechanisms will be contrasted with those for myosin X, a motor with unusual in vivo motility that suggests a novel form of strain sensing. The long term goal of this research is to reveal how motors, and systems of motors, have been optimized for their cellular trafficking tasks. Myosin motility is required for various normal and pathological cell functions, including development of polarized cellular structures, formation of cellular adhesions and tissue development, wound healing, intracellular trafficking, and cell division. This research will address critical questions about the underlying biology behind motor-related disease, including, among others, several forms of inherited deafness related to the proper development and maintenance of stereo cilia in sensory hair cells.