Department of Biochemistry, Molecular Biology & Biophysics, University of Minnesota, Minneapolis, MN, USA.
Department of Physiology and Biophysics, Virginia Commonwealth University, Richmond, VA, USA.
Nat Commun. 2024 Jun 15;15(1):5120. doi: 10.1038/s41467-024-48951-5.
Calmodulin transduces [Ca] information regulating the rhythmic Ca cycling between the sarcoplasmic reticulum and cytoplasm during contraction and relaxation in cardiac and skeletal muscle. However, the structural dynamics by which calmodulin modulates the sarcoplasmic reticulum Ca release channel, the ryanodine receptor, at physiologically relevant [Ca] is unknown. Using fluorescence lifetime FRET, we resolve different structural states of calmodulin and Ca-driven shifts in the conformation of calmodulin bound to ryanodine receptor. Skeletal and cardiac ryanodine receptor isoforms show different calmodulin-ryanodine receptor conformations, as well as binding and structural kinetics with 0.2-ms resolution, which reflect different functional roles of calmodulin. These FRET methods provide insight into the physiological calmodulin-ryanodine receptor structural states, revealing additional distinct structural states that complement cryo-EM models that are based on less physiological conditions. This technology will drive future studies on pathological calmodulin-ryanodine receptor interactions and dynamics with other important ryanodine receptor bound modulators.
钙调蛋白将[Ca]信息转导到心脏和骨骼肌肉的收缩和松弛期间，调节肌浆网和细胞质之间的节律性 Ca 循环。然而，在生理相关[Ca]下，钙调蛋白调节肌浆网 Ca 释放通道（ryanodine 受体）的结构动力学仍不清楚。我们使用荧光寿命 FRET 解析钙调蛋白的不同结构状态以及钙调蛋白与ryanodine 受体结合构象的变化。骨骼肌和心肌 ryanodine 受体同工型表现出不同的钙调蛋白-ryanodine 受体构象，以及结合和结构动力学，分辨率为 0.2ms，这反映了钙调蛋白的不同功能作用。这些 FRET 方法提供了对生理钙调蛋白-ryanodine 受体结构状态的深入了解，揭示了其他不同的结构状态，补充了基于较少生理条件的 cryo-EM 模型。这项技术将推动未来对病理性钙调蛋白-ryanodine 受体相互作用和与其他重要的ryanodine 受体结合调节剂的动力学的研究。
