Troponin is an essential component of striated muscle and it regulates the sliding of actomyosin system in a calcium-dependent manner. Despite its importance, the structure of troponin has been elusive due to its high structural heterogeneity. In this study, we analyzed the 3D structures of murine cardiac thin filaments using a cryo-electron microscope equipped with a Volta phase plate (VPP). Contrast enhancement by a VPP enabled us to reconstruct the entire repeat of the thin filament. We determined the orientation of troponin relative to F-actin and tropomyosin, and characterized the interactions between troponin and tropomyosin. This study provides a structural basis for understanding the molecular mechanism of actomyosin system.

中文翻译：

---

心脏细丝的Cryo-EM结构揭示了肌钙蛋白的3D结构。

肌钙蛋白是横纹肌的重要组成部分，它以钙依赖性方式调节肌动球蛋白系统的滑动。尽管其重要性，但由于肌钙蛋白的高度结构异质性，其结构却难以捉摸。在这项研究中，我们使用配备有Volta相板（VPP）的冷冻电子显微镜分析了小鼠心脏细丝的3D结构。VPP增强的对比度使我们能够重建细丝的整个重复。我们确定了肌钙蛋白相对于F-肌动蛋白和原肌球蛋白的方向，并表征了肌钙蛋白和原肌球蛋白之间的相互作用。该研究为理解肌动球蛋白系统的分子机制提供了结构基础。