Plugging interactions of HAP2 pentamer into the distal end of flagellar filament revealed by electron microscopy
Plugging interactions of HAP2 pentamer into the distal end of flagellar filament revealed by electron microscopy
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DOI：
10.1006/jmbi.1998.1663
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发表时间：
1998-04-10
影响因子：
5.6
通讯作者：
Namba, K
中科院分区：
文献类型：
--
作者：
Maki, S;Vonderviszt, F;Namba, K
细菌鞭毛的末端有一个紧密附着的帽状结构。帽是HAP 2蛋白（也称为FID）的寡聚体组装体，并且通过防止鞭毛蛋白单体在没有聚合的情况下泄漏而在体内丝状体生长中起重要作用。在溶液中形成的HAP 2复合物的电子显微镜照片仅显示了一个五边形形状，称为“星帽”，这被认为是帽的端视图。分子量大致对应于HAP 2的十二聚体，因此双层星帽被建模为帽。在这里，我们已经观察到的电子显微镜照片的配合物的侧视图。图像清楚地显示了一个矩形形状，约80埃宽，180埃长，在其长轴上具有双极特征，表明该复合物是一对双极五聚体。在颗粒的每一端都识别出薄板特征，其看起来与观察到的天然丝帽结构完全相同。结合之前通过电子低温显微镜分析的细丝结构，结果表明帽是一个五聚体，其薄板暴露于溶剂中，另一半插入细丝远端的孔中，该孔几乎是其中心通道的两倍宽。这也使我们能够模拟鞭毛蛋白亚基在丝状体中的轴向结构域排列。(C)出版社：Academic Press Limited。
Bacterial flagellum has a cap structure tightly attached to its distal end. The cap is an oligomeric assembly of HAP2 protein (also called FID) and plays an essential role in the filament growth in vivo by preventing flagellin monomers from leaking out without polymerization. Electron micrographs of the HAP2 complex formed in solution showed exclusively a pentagonal shape, called "star-cap", which was thought to be the end-on view of the cap. The molecular mass roughly corresponded to a dodecamer of HAP2 and therefore a double-layered star-cap was modeled to be the cap. Here, we have observed the side view of the complex in electron micrographs. The images clearly show a rectangular shape, about 80 Angstrom wide and 180 Angstrom long, with a bipolar feature in its long axis, indicating that the complex is a bipolar pair of pentamers. A thin plate feature is identified at each end of the particle, which looks exactly like the one observed as the structure of the native filament cap. Together with the structure of the filament previously analyzed by electron cryomicroscopy, the results suggest that the cap is a pentamer with its thin plate exposed to the solvent and the other half Plugged into the hole at the distal end of the filament, which is almost twice wider than its central channel. This also allows us to model the axial domain arrangement of flagellin subunit in the filament. (C) 1998 Academic Press Limited.