Ishikawa Takashi
Laboratory of Biomolecular Research, Paul Scherrer Institute, 5232 Villigen PSI, Switzerland.
Department of Biology, ETH Zurich, 5232 Villigen PSI, Switzerland.
Cold Spring Harb Perspect Biol. 2017 Jan 3;9(1):a028076. doi: 10.1101/cshperspect.a028076.
The axoneme is the main extracellular part of cilia and flagella in eukaryotes. It consists of a microtubule cytoskeleton, which normally comprises nine doublets. In motile cilia, dynein ATPase motor proteins generate sliding motions between adjacent microtubules, which are integrated into a well-orchestrated beating or rotational motion. In primary cilia, there are a number of sensory proteins functioning on membranes surrounding the axoneme. In both cases, as the study of proteomics has elucidated, hundreds of proteins exist in this compartmentalized biomolecular system. In this article, we review the recent progress of structural studies of the axoneme and its components using electron microscopy and X-ray crystallography, mainly focusing on motile cilia. Structural biology presents snapshots (but not live imaging) of dynamic structural change and gives insights into the force generation mechanism of dynein, ciliary bending mechanism, ciliogenesis, and evolution of the axoneme.
轴丝是真核生物中纤毛和鞭毛的主要细胞外部分。它由微管细胞骨架组成，通常包括九个双联管。在运动性纤毛中，动力蛋白ATP酶运动蛋白在相邻微管之间产生滑动运动，这些运动整合为精心编排的摆动或旋转运动。在初级纤毛中，有许多感觉蛋白在围绕轴丝的膜上发挥作用。在这两种情况下，正如蛋白质组学研究所阐明的，在这个分区化的生物分子系统中存在数百种蛋白质。在本文中，我们回顾了使用电子显微镜和X射线晶体学对轴丝及其组件进行结构研究的最新进展，主要关注运动性纤毛。结构生物学呈现了动态结构变化的快照（而非实时成像），并深入了解了动力蛋白的力产生机制、纤毛弯曲机制、纤毛发生以及轴丝的进化。
