High Resolution Electron Microscope for Structural Biology

本研究旨在阐明肌球蛋白和肌动蛋白分子在肌肉（以及许多其他运动系统）中的相互作用产生力的机制，并将重点放在横纹肌收缩过程中交叉桥发生变化的动力学上。长期以来，人们已经确定肌肉收缩是由一种滑动丝机制引起的，其中肌动蛋白和肌球蛋白丝的部分重叠阵列受到相对滑动力的作用，导致肌肉缩短。一般认为，这种力是由肌凝蛋白桥与肌动蛋白丝上的位点的循环相互作用产生的。然而，这一过程的结构细节已被证明是特别难以确定的，部分原因是许多正在发生的变化具有短暂和不同步的性质，部分原因是获取任何快速变化的生物系统的亚微观结构信息在技术上存在困难。由Heuser和其他人开发的快速冻结技术，现在原则上可以获得这些瞬态结构状态的电子显微镜图像，并且将开发这些技术的适当变体，以便与时间分辨x射线衍射研究得出的证据建立相关性。​这些方法应该提供重要的新信息，关于桥的结构行为，因为他们与肌动蛋白相互作用和发展力。当与生化和生理学研究的新信息相结合时，本工作的结果将极大地促进我们对这一非常基本的生物学机制的理解。

This research is intended to elucidate the mechanism by which force is developed by the interaction of myosin and actin molecules in muscle (and in a number of other motile systems) and will focus on the dynamics of the changes taking place in the crossbridges in striated muscle during contraction. It has long been established that muscle contraction is brought about by a sliding filament mechanism, in which partially overlapping arrays of actin and myosin filaments are acted on by a relative sliding force which leads to shortening of the muscle. It is generally believed that this force is generated by a cyclic interaction of myosin crossbridges with sites on the actin filaments. However, the structural details of the process have proved to be particularly difficult to establish, partly because of the transient and unsynchronized nature of many of the changes taking place, and partly because of the technical difficulty of obtaining submicroscopic structural information about any rapidly changing biological system. The development of rapid freezing techniques by Heuser and others has now made it possible in principle to obtain electron microscope images of these transient structural states and suitable variations of these techniques will be developed to enable correlations to be made with evidence derived from time-resolved x-ray diffraction studies. These approaches should provide important new information about the structural behavior of the crossbridges as they interact with actin and develop force. When combined with new information from biochemical and physiological studies, the results of the present work should materially advance our understanding of this very fundamental biological mechanism.