THIN FILAMENTS AND MUSCLE REGULATION

细丝相关调节蛋白控制肌动球蛋白 各种肌肉和非肌肉收缩系统中的相互作用。 在脊椎动物的横纹肌中，调节蛋白复合体 原肌球蛋白和肌钙蛋白与细丝中的肌动蛋白相连 阻断肌球蛋白与肌动蛋白的交叉桥结合实现松弛 钙离子的缺乏。在平滑肌中，细丝相关蛋白 (原肌球蛋白、钙调蛋白和可能的降钙素)可能在 与众所周知的钙-钙调蛋白结合或补充- 肌球蛋白磷酸化过程对肌动球蛋白ATPase的调节 并因此产生和/或维护张力。在非肌肉领域 与肌动蛋白相连的钙调蛋白系统，可能与肌球蛋白协同作用 磷酸化，也调节肌动球蛋白依赖的细胞质 能动性。钙调蛋白-原肌球蛋白复合体，如肌钙蛋白-原肌球蛋白， 在细胞内低浓度时抑制肌动球蛋白ATPase，而 原肌球蛋白本身增强了ATPase。我们将研究分子 细丝连接蛋白影响肌动球蛋白的机制 通过研究蛋白质在细丝上的结构相互作用 来自不同类型的肌肉和其他细胞。电子显微镜 (包括冷冻显微镜)、计算机辅助图像分析和三个- 将使用空间重建来确定细丝 结构并评估Thin的结构排列的变化 灯丝成分处于“开”和“关”状态。的重建工作 肌钙蛋白和Caidesmon基天然细丝以及 由这些组分重组的合成纤维的重建 将进行这些系统中的一个，以确定肌钙蛋白的影响， 原肌球蛋白、双结构域肌动蛋白中钙离子和钙蛋白的作用 结构，以及肌动球蛋白结合。高精度的重建 将适用于F-肌动蛋白的原子图，以详细说明特定的原子 调节蛋白与F-肌动蛋白功能结构域之间的联系。 我们自己和其他人发布的重建演示了 这些目标的可行性。我们预计我们继续的结构 研究将有助于阐明其分子机制。 肌钙蛋白在骨骼肌中的作用，并有助于 了解钙调蛋白和降钙素在动脉粥样硬化中的作用和机制 平滑肌肉收缩反应的微调。一个大女人 对参与调控的分子机制的理解 健康组织的收缩性能可能有助于未来对缺陷的评估 发生在一些疾病的过程中。浅谈对肌肉的控制 例如，收缩在调节血管紧张性方面非常重要。 血管张力和肺气道阻力，在许多决定因素中 高血压和哮喘等疾病的风险。此外，将军 我们的目标的重要性被强调的可能性是 与非肌肉微丝相连的钙调蛋白可能在 控制细胞质的运动过程，如胞质分裂和 因此可能参与调节正常和正常的细胞分裂 癌细胞。

Thin filament-associated regulatory proteins control actomyosin interactions in a variety of muscle and non-muscle contractile systems. In vertebrate striated muscle, the regulatory protein complex of tropomyosin and troponin linked to actin in the thin filaments causes relaxation by blocking strong myosin-crossbridge binding onto actin in the absence of Ca2+. In smooth muscle, thin filament-associated proteins (tropomyosin, caldesmon and possibly calponin) may function in conjunction with or in addition to the well-known Ca2+-calmodulin- dependent myosin phosphorylation process to modulate actomyosin ATPase and consequently tension generation and/or maintenance. In non-muscle systems, caldesmon linked to actin may, in concert with myosin phosphorylation, also act to regulate actomyosin-dependent cytoplasmic motility. The caldesmon-tropomyosin complex, like troponin-tropomyosin, inhibits actomyosin ATPase at low intracellular Ca2+-concentration, while tropomyosin itself potentiates ATPase. We will investigate the molecular mechanisms by which thin filament-linked proteins influence actomyosin by studying The structural interactions of the proteins on thin filaments from different types of muscles and other cells. Electron microscopy (including cryomicroscopy), computer-assisted image analysis and three- dimensional reconstruction will be used to determine thin filament structure and to evaluate changes in the structural arrangement of thin filament components in "on-" and in "off-states". Reconstruction of troponin- and caidesmon-based native thin filaments as well as reconstruction of synthetic filaments reconstituted from the components of these systems will be carried out to determine the impact of troponin, caldesmon and calponin on tropomyosin position, two-domain actin structure, and on actomyosin-binding. Reconstructions of high precision will be fitted to the atomic map of F-actin to detail specific atomic contacts between regulatory proteins and functional domains on F-actin. Our own published reconstructions and those of others demonstrate the feasibility of these goals. We anticipate that our continued structural studies will lead to an elucidation of the molecular mechanism of troponin action in skeletal muscle and contribute towards an understanding of the role and mechanism of caldesmon and calponin in the fine tuning of the contractile response in smooth muscle. A broad understanding of the molecular mechanisms involved in the regulation of contractility in healthy tissue may aid in future evaluation of defects occurring in some disease procosses. The control of smooth muscle contractility, for example, is of great importance in the regulation of vascular tone and pulmonary airway resistance, determinants in a number of conditions such as hypertension and asthma. Moreover, the general significance of our goals is underscored by the possibility that caldesmon linked to non-muscle microfilaments may have a role in controlling cytoplasmic motile processes such as cytokinesis, and therefore may be involved in regulating cell division in normal and cancer cells.