Molecular mechanisms of muscle contraction

背景。肌肉收缩是由附着在肌动蛋白丝上的分子运动肌球蛋白II驱动的。肌球蛋白分子将从三磷酸腺苷（ATP）中提取的化学能转化为机械能。在肌凝蛋白和肌动蛋白之间的初始附着后，ATP被水解，磷酸（Pi）和随后的ADP从肌凝蛋白中释放出来。分子经历构象变化——能量冲程——产生力并使肌动蛋白丝滑动。ATP释放的化学能转化为肌球蛋白力量卒中，并将其放大为肌肉收缩的分子机制尚不清楚。* * *长期目标。这项研究计划的长期目标是了解肌肉收缩和力量产生的分子和细胞机制。本提案的具体目标是：***1 -确定肌凝蛋白结构与肌动蛋白滑动之间的关系***2 -确定肌凝蛋白负责将化学能转化为机械功的亚结构***3 -确定肌凝蛋白分子在细丝中协同工作时的新特性。这个研究项目将使用我实验室开发的各种实验系统和技术。肌凝蛋白分子的结构域和子结构域被假设用来定义强力中风。在特定的目标(1)中，我们将实验天然肌凝蛋白分子和肌凝蛋白突变体，其中一些亚结构域已经耗尽。分子将被测试与运动论文，允许测量肌动蛋白滑动的速度。在特定目标(2)中，分子（原生和突变）将在高速原子力显微镜（HS-AFM）下进行测试，该显微镜允许在观察肌球蛋白-肌动蛋白系统结构变化的同时测量力。在特定的目的(3)分子（原生和突变）将被聚合成不同浓度的细丝，以评估肌球蛋白协同工作的新特性。这些细丝将使用纳米制造的悬臂系统进行力测量测试。* * *的意义。理解肌凝蛋白力量冲程——肌肉收缩的最基本步骤——对于理解肌肉收缩是必不可少的，肌肉收缩是生命的基本功能。除了收缩机制外，肌球蛋白II是众多分子马达（如运动蛋白、动力蛋白、肌球蛋白V）中的一种，具有多种生理功能。分子马达有几个相似之处，包括动力冲程诱导的运动和动力产生。因此，了解肌球蛋白II的机制将有助于深入了解分子马达的功能，对生物学具有深远的意义

Background. Muscle contraction is driven by the molecular motor myosin II while attached to actin filaments. Myosin molecules transform chemical energy extracted from adenosine tri-phosphate (ATP) into mechanical work. After an initial attachment between myosin and actin, ATP is hydrolyzed, and phosphate (Pi) and subsequently ADP are released from myosin. The molecule undergoes a conformational change - the power stroke - producing force and sliding the actin filament. The molecular mechanisms behind the conversion of chemical energy released from ATP into the myosin power stroke, and its amplification into muscle contraction is not well understood. ***Long-term objective. The long-term objective of this research program is to understand the molecular and cellular mechanisms of muscle contraction and force generation. The specific goals of this proposal are:***1 - To determine the relation between myosin structures and actin sliding ***2 - To determine the sub-structures of myosin responsible for converting chemical energy into mechanical work ***3 - To determine the emerging properties of myosin molecules when working cooperatively in filaments.***Methods. This research program will use a variety of experimental systems and techniques developed in my laboratory. There are domains and sub-domains of the myosin molecule that have been hypothesized to define the power stroke. In specific aim (1) we will experiment with native myosin molecules and also myosin mutants in which some of these sub-domains have been depleted. Molecules will be tested with a motility essay, that allows for measurements of velocity of actin sliding. In specific aim (2) the molecules (native and mutants) will be tested under a High-Speed Atomic Force Microscope (HS-AFM), that allows measurements of force while visualizing structural changes in the myosin-actin system. In specific aim (3) molecules (native and mutants) will be polymerized into filaments in different concentrations, to evaluate the emerging properties of myosins working cooperatively. The filaments will be tested for force measurements using a system of nanofabricated cantilevers. ***Significance. Understanding the myosin power stroke - the most fundamental step of muscle contraction - is essential for understanding muscle contraction, a basic function of life. Beyond the mechanisms of contraction, myosin II is one among many molecular motors (e.g. kinesin, dynein, myosin V), with a variety of physiological functions. Molecular motors share several similarities, including a power-stroke induced motility and force production. Therefore, understanding myosin II mechanisms will provide insight into the functioning of molecular motors in general, with far-reaching implications for biology.**