STRUCTURAL BASES OF REGULATION OF SKELETAL MUSCLE

Muscle contraction is regulated by both Ca2+ dependent thin filament activation and mechanosensing-based thick filament activation that switches ON the motors in relation to the load. Evidence is growing for the involvement in thick filament regulation of the cytoskeleton protein titin, which runs from the midpoint of the thick filament to the end of the sarcomere, and the myosin binding protein C (MyBP-C), which is bound to the backbone of the thick filament in its central one-third and bridges thin and thick filaments. We use X-ray diffraction to investigate MyBP-C role in inter-filament communication and titin role in thick filament mechanosensing. The experiments, conducted in intact frog skeletal muscle fibres, exploit the finding that X-ray fine structure of myosin based reflections reports the footprints of both MyBP-C and titin and represent a testbed for future investigation on skinned fibres and whole muscles of rodent models with mutations in specific proteins.

肌肉收缩受到双重调控：钙离子依赖的细丝激活与基于机械感知的粗丝激活，后者可根据负荷状态激活肌球蛋白马达。越来越多的证据表明，细胞骨架蛋白肌联蛋白（titin）与肌球蛋白结合蛋白C（MyBP-C）参与了粗丝的调控过程：肌联蛋白从粗丝中点延伸至肌节（sarcomere）末端；肌球蛋白结合蛋白C结合于粗丝主干的中央三分之一区段，并介导细丝与粗丝之间的连接。本研究采用X射线衍射（X-ray diffraction）技术，探究肌球蛋白结合蛋白C在丝间信号传导中的作用，以及肌联蛋白在粗丝机械感知中的功能。本实验以完整的青蛙骨骼肌纤维为研究对象，利用了如下核心发现：肌球蛋白衍射峰的X射线精细结构能够反映肌球蛋白结合蛋白C与肌联蛋白的作用踪迹，该实验体系可为未来针对携带特定蛋白突变的啮齿类动物模型的透化肌纤维及完整肌肉的相关研究提供测试平台。