STRUCTURAL BASIS OF SMOOTH MUSCLE CONTRACTION

平滑肌是人体正常运转必不可少的， 在血管、呼吸、消化和其他功能中起重要作用。 平滑肌功能障碍与重大疾病有关， 高血压、哮喘和动脉硬化。平滑肌收缩是 最终是肌动蛋白丝滑过肌球蛋白的结果 细丝。 本项目的长期目标是阐明 平滑肌收缩的结构基础及其调节 分子水平。 令人兴奋的平滑肌功能的新见解最近成为 可能通过解决几个收缩的晶体结构， 以及电子显微镜的最新进展 和图像处理。 我们将利用这些进步， 具体目的如下：（1）定义三维 天然平滑肌肌球蛋白的分子结构和组成 （2）确定侧极性的分子基础 平滑肌肌球蛋白丝的结构和结构 SM 1和SM 2肌球蛋白亚型的意义;（3）确定三种- 平滑肌中肌动蛋白丝的三维分子结构; （4）阐明肌动蛋白的三维结构， 平滑肌细胞中的肌球蛋白丝，以及 他们的互动。 电子显微镜将用于确定分子结构 肌动蛋白和肌球蛋白丝的结构变化， 伴随着收缩。 肌肉丝将被保存在接近 他们的国家使用最先进的技术，他们的三个- 三维结构将通过螺旋或断层扫描来计算 重建 对细丝结构的近原子理解， 通过对原子结构的拟合，得到了它与功能的关系 肌动蛋白和肌球蛋白头的细丝结构， 电镜 对分子组装的新的结构见解， 组织和功能将获得使用互补分子 生物学和免疫学方法。 血管和 将研究胃肠道平滑肌模型系统。 的 该项目的结果应提供基本的见解， 平滑肌收缩和调节的分子机制，以及 转化为疾病状态下可能发生的结构变化。 初步 数据显示我们的目标的可行性。

Smooth muscle is essential to the normal operation of the body, playing crucial roles in vascular, respiratory, digestive, and other functions. Malfunction of smooth muscle is implicated in major diseases such as hypertension, asthma and arteriosclerosis. Smooth muscle contraction is ultimately a result of the sliding of actin filaments past myosin filaments. The long term objective of this project is to elucidate the structural basis of smooth muscle contraction and its regulation at the molecular level. Exciting new insights into smooth muscle function have recently become possible by solution of the crystal structures of several contractile and regulatory proteins and by recent advances in electron microscopy and image processing. We will take advantage of these advances to carry out the following Specific Aims: (1) To define the three-dimensional molecular architecture and composition of native smooth muscle myosin filaments; (2) To determine the molecular basis of the side-polar structure of smooth muscle myosin filaments and the structural significance of SM1 and SM2 myosin isoforms; (3) To determine the three- dimensional molecular structure of the actin filaments in smooth muscle; and (4) To elucidate the three-dimensional organization of the actin and myosin filaments in smooth muscle cells, and the structural basis of their interaction. Electron microscopy will be used to determine the molecular structure of the actin and myosin filaments, and the structural changes that accompany contraction. Muscle filaments will be preserved in close-to their native states using state-of-the-art techniques, and their three- dimensional structures will be computed by helical or tomographic reconstruction. A near-atomic understanding of filament structure and its relation to function will be gained by fitting the atomic structures of actin and the myosin head to the filament structures determined by electron microscopy. Novel structural insights into molecular assembly, organization and function will be obtained using complementary molecular biological and immunological approaches. Both vascular and gastrointestinal smooth muscle model systems will be studied. The results of this project should provide fundamental insights into the molecular mechanism of smooth muscle contraction and regulation, and into structural changes that may occur in diseased states. Preliminary data are presented showing the feasibility of our goals.