SINGLE MOLECULAR MECHANICS OF MYOSIN V

基于肌动蛋白和肌球蛋白的运动系统参与了广泛的细胞运动功能，包括细胞器运输、变形体运动和细胞分裂。已发现的肌球蛋白有多种类型，它们都有一个共同的具有肌动蛋白结合和ATP水解活性的酶运动域。然而，颈部区域在长度和结合轻链的能力上有所不同。这项建议涉及一种最近发现的肌球蛋白，肌球蛋白V(M5)。M5有一个细长的颈部区域，有可能结合六条轻链。有人提出，颈部作为一个刚性的水平臂，通过放大运动域中的小动作来产生运动和力，从而产生运动和力。在这项提议中，水平臂假说将通过测试具有不同颈部长度的突变M5分子来检验。在老鼠和人类身上，已经发现了几种影响神经功能和色素沉积的突变。这些突变表明M5在细胞器运输中发挥作用。细胞器马达通常是进行性的。在这项提议中，将通过研究单个M5分子在每次扩散相遇时在肌动蛋白轨迹上采取多个步骤的能力来确定单个M5分子是否具有进行性。

Actin and myosin based motile systems are involved in a wide range of cellular motile functions including organelle transport, ameboid motion and cell division. Many types of myosin have been discovered all of which share a common enzymatic motor domain with actin binding and ATP hydrolytic activity. However, the neck regions differ in length and their ability to bind light chains. This proposal is concerned with a recently discovered myosin, Myosin V (M5). M5 has an elongated neck region with the potential to bind six light chains. It has been proposed that the neck acts as a rigid level arm that produces movement and force that produces movement and force by amplifying small movements in the motor domain. In this proposal the level arm hypothesis will be tested by testing mutant M5 molecules with varying neck lengths. In mice and humans, several mutations that affect neural function and pigment deposition have been identified. These mutations suggest a role for M5 in organelle transport. Organelle motors are typically processive. In this proposal it will be determined if a single M5 molecule is processive by studying its ability to take multiple steps on an actin track per diffusional encounter.