Biomolecular Research Laboratory, Paul Scherrer Institute, 5232 Villigen PSI, Switzerland.
J Cell Biol. 2011 Nov 14;195(4):673-87. doi: 10.1083/jcb.201106125. Epub 2011 Nov 7.
Radial spokes (RSs) are ubiquitous components in the 9 + 2 axoneme thought to be mechanochemical transducers involved in local control of dynein-driven microtubule sliding. They are composed of >23 polypeptides, whose interactions and placement must be deciphered to understand RS function. In this paper, we show the detailed three-dimensional (3D) structure of RS in situ in Chlamydomonas reinhardtii flagella and Tetrahymena thermophila cilia that we obtained using cryoelectron tomography (cryo-ET). We clarify similarities and differences between the three spoke species, RS1, RS2, and RS3, in T. thermophila and in C. reinhardtii and show that part of RS3 is conserved in C. reinhardtii, which only has two species of complete RSs. By analyzing C. reinhardtii mutants, we identified the specific location of subsets of RS proteins (RSPs). Our 3D reconstructions show a twofold symmetry, suggesting that fully assembled RSs are produced by dimerization. Based on our cryo-ET data, we propose models of subdomain organization within the RS as well as interactions between RSPs and with other axonemal components.
放射辐条（RSs）是 9+2 轴丝中普遍存在的组成部分，被认为是参与对动力蛋白驱动的微管滑动进行局部控制的机械化学转导器。它们由>23 种多肽组成，其相互作用和位置必须被破译才能理解 RS 的功能。在本文中，我们使用冷冻电子断层扫描（cryo-ET）获得了衣滴虫纤毛和莱茵衣藻鞭毛中 RS 在原位的详细三维（3D）结构。我们阐明了三种辐条物种（RS1、RS2 和 RS3）在嗜热四膜虫和莱茵衣藻中的相似性和差异性，并表明 RS3 的一部分在莱茵衣藻中是保守的，而莱茵衣藻只有两种完整的 RS 物种。通过分析莱茵衣藻突变体，我们确定了 RS 蛋白（RSPs）亚群的特定位置。我们的 3D 重建显示出二倍对称性，表明完全组装的 RS 是通过二聚化产生的。基于我们的 cryo-ET 数据，我们提出了 RS 内亚区结构的模型以及 RSPs 与其他轴丝成分之间的相互作用模型。
