Mechanisms of Processivity in Molecular Motors

分子马达的过程机制

• 批准号: 6863761
• 负责人: STEVEN S ROSENFELD
• 金额: $ 3.42万
• 依托单位: UNIVERSITY OF ALABAMA AT BIRMINGHAM
• 依托单位国家: 美国
• 财政年份: 2004
• 资助国家: 美国
• 起止时间: 2004-03-01 至 2005-03-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6863761
• 关键词: active sites; adenosinetriphosphatase; allosteric site; dimer; enzyme mechanism; enzyme model; fluorescence resonance energy transfer; gel mobility shift assay; green fluorescent proteins; hybrid enzyme; intracellular transport; kinesin; molecular dynamics; molecular probes; myosins; nucleotides; physiologic stressor; protein protein interaction; protein structure function; protein transport; spectrometry; time resolved data

DESCRIPTION (provided by applicant): Myosins and kinesins make up a diverse collection of molecular motors that generate force and movement at the expense of nucleotide hydrolysis. Despite the fact that these two motor superfamilies share little primary structure, members of each group often serve similar functions within the cell. For example, while some myosins and kinesins transport vesicles, others generate the cortical tension required to maintain the cytoskeleton and the mitotic apparatus. The central hypothesis of this project is that the physiologic demands placed on a motor determine how it behaves as an enzyme. It should therefore be possible to predict key aspects of a motor's enzymology if its function within the cell is known. Myosin V and conventional kinesin transport vesicles relatively long distances and work as single motors in isolation. Consistent with the central hypothesis, these two motors share at least one feature of their enzymology--both are processive. Processivity would be necessary for vesicle transporters that work in isolation, since premature dissociation could have dire physiologic consequence. Thus, processivity serves as an example of how a motor's enzymology can be shaped by its physiology. In this proposal, I will expand on this theme of processivity as a response to physiologic demands. I will use the data I have generated with kinesin to formulate a model of how processivity works in molecular motors, and will test this model by comparing kinesin to myosin V. In particular, I will examine three components of molecular motor enzymology whose features should be predictable for vesicle transporters that work in isolation. These include the timing of the forward step, the flexibility of the motor's mechanical element, and the mechanism of allosteric communication. Taken together, these components are likely to determine how processive a motor is, and like processivity itself, they too should be shaped by the demands of physiology. Determining how closely these components conform to the predictions based on physiology will therefore provide a critical test of the central hypothesis. Furthermore, if successful, this work will support the argument that understanding how a motor works in vitro as an enzyme can provide valuable insights into how it works in vivo in the cell.

描述（由申请人提供）：肌球蛋白和驱动蛋白组成了多种分子马达，它们以核苷酸水解为代价产生力和运动。尽管这两个运动超家族的一级结构几乎没有共同之处，但每个组的成员通常在细胞内发挥相似的功能。例如，虽然一些肌球蛋白和驱动蛋白运输囊泡，但其他肌球蛋白和驱动蛋白产生维持细胞骨架和有丝分裂装置所需的皮质张力。该项目的中心假设是，对马达的生理需求决定了它作为酶的行为方式。因此，如果知道马达在细胞内的功能，就应该可以预测马达酶学的关键方面。肌球蛋白 V 和传统的驱动蛋白运输囊泡的距离相对较长，并且作为孤立的单个马达工作。与中心假设一致，这两种马达至少有一个酶学特征——都是过程性的。对于单独工作的囊泡转运蛋白来说，持续合成能力是必要的，因为过早解离可能会产生可怕的生理后果。因此，持续性是发动机的酶学如何通过其生理学来塑造的一个例子。在本提案中，我将扩展持续性这一主题，作为对生理需求的回应。 我将使用我用驱动蛋白生成的数据来制定分子马达中持续性如何工作的模型，并将通过比较驱动蛋白和肌球蛋白 V 来测试该模型。特别是，我将检查分子马达酶学的三个组成部分，其特征应该是对于单独工作的囊泡转运蛋白是可预测的。这些包括前进的时间、电机机械元件的灵活性以及变构通信机制。总而言之，这些组件很可能决定电机的加工能力，并且像加工能力本身一样，它们也应该根据生理学的要求来塑造。因此，确定这些成分与基于生理学的预测的符合程度将为中心假设提供关键检验。此外，如果成功，这项工作将支持这样的论点：了解马达如何作为酶在体外发挥作用，可以为了解其在细胞体内如何发挥作用提供有价值的见解。