STRUCTURAL BASIS OF SMOOTH MUSCLE CONTRACTION

平滑的肌肉对于身体的正常运作是必不可少的，发挥 在血管、呼吸、消化和其他功能中起关键作用。 平滑肌功能障碍与重大疾病有关，如 高血压、哮喘和动脉硬化。平滑肌肉收缩是 最终是肌动蛋白细丝滑过肌球蛋白的结果 细丝。这个项目的长期目标是阐明 节段性肌肉收缩的结构基础及其调控 分子水平。 最近对平滑肌功能有了令人兴奋的新见解 通过解几个收缩的晶体结构是可能的 和调节蛋白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来进行 提出了以下具体目标：(1)界定立体 天然平滑肌肌球蛋白的分子结构和组成 长丝；(2)确定侧极性的分子基础 肌球蛋白肌球蛋白细丝的结构及其结构 SM1和SM2肌球蛋白亚型的意义； 肌动蛋白细丝的三维分子结构； 以及(4)阐明肌动蛋白的三维结构和 平滑肌细胞中的肌球蛋白细丝及其结构基础 他们的互动。 电子显微镜将被用来确定分子结构 肌动蛋白和肌球蛋白细丝的结构变化 伴随着收缩。肌丝将在近距离保存 他们的家乡使用最先进的技术，他们的三个- 空间结构将通过螺旋或层析成像进行计算 重建。对灯丝结构和结构的近原子理解 它与功能的关系将通过对原子结构的拟合来获得 肌动蛋白和肌球蛋白头部对细丝结构的影响 电子显微镜。对分子组装的新的结构洞察， 将使用互补分子获得组织和功能 生物学和免疫学方法。无论是血管和 将对胃肠平滑肌模型系统进行研究。这个 这个项目的结果应该为我们提供对 平滑肌收缩和调节的分子机制，以及 转化为在患病状态下可能发生的结构性变化。初步 数据显示了我们目标的可行性。

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.