Outer doublet heterogeneity reveals structural polarity related to beat direction in Chlamydomonas flagella.
Outer doublet heterogeneity reveals structural polarity related to beat direction in Chlamydomonas flagella.
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DOI：
10.1083/jcb.97.3.902
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发表时间：
1983-09
期刊：
影响因子：
--
通讯作者：
Witman GB
中科院分区：
文献类型：
--
作者：
Hoops HJ;Witman GB
衣原体鞭毛的连续横截面分析揭示了轴丝中的几个结构不对称性。其中一个双联体缺少外动力蛋白臂，在其B-小管中有一个喙状突起，并有一个由两部分组成的桥，从该双联体的A-小管延伸到相邻双联体的B-小管。与缺少臂的双峰正对面的两个双峰在它们的B小管中具有喙状突起。这些不对称总是发生在相同的双峰从部分到部分，表明某些双峰具有一致的形态专业化。这些独特的双峰赋予轴丝固有的结构极性。所有这三种特化都存在于轴丝的近端部分;基于它们在孤立轴丝的随机横截面中的频率，两部分桥和喙状突起分别存在于轴丝的近端四分之一和一半，并且外臂不存在于大于轴丝长度的90%的一个双峰中。每个鞭毛的外部无臂的双峰面向另一个鞭毛，表明每个轴丝相对于其有效行程的方向具有相同的旋转方向。这有力地表明，有效中风的方向是由轴丝内的结构组件控制。条纹纤维与特定的三联体相关，表明它们在建立或维持两个鞭毛的180度旋转对称性方面发挥作用。
Analysis of serial cross-sections of the Chlamydomonas flagellum reveals several structural asymmetries in the axoneme. One doublet lacks the outer dynein arm, has a beak-like projection in its B-tubule, and bears a two-part bridge that extends from the A-tubule of this doublet to the B-tubule of the adjacent doublet. The two doublets directly opposite the doublet lacking the arm have beak-like projections in their B-tubules. These asymmetries always occur in the same doublets from section to section, indicating that certain doublets have consistent morphological specializations. These unique doublets give the axoneme an inherent structural polarity. All three specializations are present in the proximal portion of the axoneme; based on their frequency in random cross-sections of isolated axonemes, the two-part bridge and the beak-like projections are present in the proximal one quarter and one half of the axoneme, respectively, and the outer arm is absent from the one doublet greater than 90% of the axoneme's length. The outer arm-less doublet of each flagellum faces the other flagellum, indicating that each axoneme has the same rotational orientation relative to the direction of its effective stroke. This strongly suggests that the direction of the effective stroke is controlled by a structural component within the axoneme. The striated fibers are associated with specific triplets in a manner suggesting that they play a role in setting up or maintaining the 180 degrees rotational symmetry of the two flagella.