Structure of phosphorylase kinase. A three-dimensional model derived from stained and unstained electron micrographs.
Structure of phosphorylase kinase. A three-dimensional model derived from stained and unstained electron micrographs.
复制标题
磷酸化酶激酶的结构。
DOI：
10.1006/jmbi.1994.1476
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发表时间：
1994
影响因子：
5.6
通讯作者：
Carlson,GM
中科院分区：
文献类型：
--
作者：
Norcum,MT;Wilkinson,DA;Carlson,MC;Hainfeld,JF;Carlson,GM
磷酸化酶激酶是最早发现的蛋白激酶，是糖原代谢的关键调节酶。虽然它的生化特性得到了很好的表征，其三维结构和亚基拓扑结构的细节还有待阐明。本研究描述了在负染色和未染色的电子显微照片中观察到的十六聚体全酶（α4β4γ4δ4）的四个特征视图。主要的观点是广泛报道的“蝴蝶”，两个翼状的裂片由薄桥连接，以及先前描述的“圣杯”，由“杯”和“茎”部分组成。另外两个视图，一个“立方体”，类似于以前报道的“四分体”，和一个“十字”或“X”是不太常见的，但说明了粒子的整体几何形状。基于这些图像，已经构建了酶的第一个三维模型。它由四个相同的原聚体组成，与D2对称性相关，形成两个主要的结构元素（两个裂片）。两个头对头排列的原体组成了每个对称的叶;为了完成全酶，一个叶被倒置并垂直于另一个叶放置。因此，整体结构具有三个2重对称轴，并且四个原聚体的排列近似于四面体。模型的每个叶对应于蝴蝶投影的一个翅膀。两个投影形成了圣杯：在叶内方向，一个叶形成了杯子，另一个形成了茎，在叶间视图中，每个叶的一半贡献了图像的每个部分。立方体和交叉投影是从蝴蝶方向旋转90°产生的。在立方体中，每个叶的远端部分分别投影。在十字架上，一个叶是交叉的，并在另一个之上。该模型解释并预测了所有观察到的显微图像。
Phosphorylase kinase, the first protein kinase discovered, is a key regulatory enzyme in glycogen metabolism. Although its biochemical properties are well characterized, details of its three-dimensional structure and subunit topology are yet to be elucidated. This study describes four characteristic views of the hexadecameric holoenzyme (α4β4γ4δ4) as observed in both negatively stained and unstained electron micrographs. The predominant views are the widely reported "butterfly" with two wing-like lobes connected by thin bridges, and the previously described "chalice", composed of "cup" and "stem" segments. Two additional views, a "cube", similar to the previously reported "tetrad", and a "cross" or "X" are less common, but illustrate the overall geometry of the particle. Based on these images, the first three-dimensional model of the enzyme has been constructed. It is composed of four identical protomers that associate with D2symmetry to form the two major structural elements (the two lobes). Two protomers in a head to head arrangement make up each symmetrical lobe; to complete the holoenzyme, one lobe is inverted and placed perpendicular to the other. Thus, the overall structure has three 2-fold axes of symmetry, and the arrangement of the four protomers approximates a tetrahedron. Each lobe of the model corresponds to a wing of the butterfly projection. Two projections form the chalice: in the intra-lobe orientation, one lobe forms the cup and the other forms the stem, and in the inter-lobe view, one-half of each lobe contributes to each segment of the image. The cube and cross projections result from 90° rotations from the butterfly orientation. In the cube, the distal portions of each lobe are projected separately. In the cross, one lobe is crossed over and is above the other. This model both accounts for and predicts all of the observed microscopic images.