Wagenknecht T, Grassucci R, Frank J, Saito A, Inui M, Fleischer S
Wadsworth Center for Laboratories and Research, New York State Department of Health, Albany 12201-0509.
Nature. 1989 Mar 9;338(6211):167-70. doi: 10.1038/338167a0.
The calcium channel responsible for the release of Ca2+ from the sarcoplasmic reticulum of skeletal muscle during excitation-contraction coupling has recently been identified and purified. The isolated calcium channel has been identified morphologically with the 'foot' structures which are associated with the junctional face membrane of the terminal cisternae of sarcoplasmic reticulum. In situ, the foot structure extends across the gap of the triad junction from the terminal cisternae of the reticulum to the transverse tubule. We describe here the three-dimensional architecture (3.7 nm resolution) of the calcium channel/foot structure from fast-twitch rabbit skeletal muscle, which we determined from electron micrographs of isolated, non-crystalline structures that had been tilted in the electron microscope. The reconstruction reveals two different faces and an internal structure in which stain accumulates at several interconnected locations, which could empty into the junctional gap of the triad junction. The detailed architecture of the channel complex is relevant to understanding both the physical path followed by calcium ions during excitation-contraction coupling and the association of the terminal cisternae and the transverse tubules in the triad junction.
在兴奋 - 收缩偶联过程中负责从骨骼肌肌浆网释放Ca2+的钙通道最近已被鉴定和纯化。已通过与肌浆网终池连接面膜相关的“足”结构在形态学上鉴定出分离的钙通道。在原位，足结构从网状终池穿过三联体连接的间隙延伸至横小管。我们在此描述了来自快速收缩兔骨骼肌的钙通道/足结构的三维结构（分辨率为3.7纳米），这是我们从在电子显微镜中倾斜的分离的非晶体结构的电子显微照片中确定的。重建显示出两个不同的面和一个内部结构，其中染色剂在几个相互连接的位置积累，这些位置可能通向三联体连接的连接间隙。通道复合体的详细结构与理解兴奋 - 收缩偶联过程中钙离子所遵循的物理路径以及三联体连接中终池和横小管的关联有关。
