Motile cilia play various important physiological roles in eukaryotic organisms including cell motility and fertility. Inside motile cilia, large motor-protein complexes called “ciliary dyneins” coordinate their activities and drive ciliary motility. The ciliary dyneins include the outer-arm dyneins, the double-headed inner-arm dynein (IDA f/I1), and several single-headed inner-arm dyneins (IDAs a, b, c, d, e, and g). Among these single-headed IDAs, one of the ciliary dyneins, IDA d, is of particular interest because of its unique properties and subunit composition. In addition, defects in this subspecies have recently been associated with several types of ciliopathies in humans, such as primary ciliary dyskinesia and multiple morphologic abnormalities of the flagellum. In this mini-review, we discuss the composition, structure, and motor properties of IDA d, which have been studied in the model organism Chlamydomonas reinhardtii, and further discuss the relationship between IDA d and human ciliopathies. In addition, we provide future perspectives and discuss remaining questions regarding this intriguing dynein subspecies.

中文翻译：

---

臂内动力蛋白亚种 d 在纤毛运动中的功能和结构意义

运动纤毛在真核生物中发挥着各种重要的生理作用，包括细胞运动和生育力。在运动纤毛内部，称为“纤毛动力蛋白”的大型运动蛋白复合物协调其活动并驱动纤毛运动。纤毛动力蛋白包括外臂动力蛋白、双头内臂动力蛋白（IDA f/I1）和几种单头内臂动力蛋白（IDA a、b、c、d、e 和 g）。在这些单头 IDA 中，纤毛动力蛋白之一 IDA d 由于其独特的性质和亚基组成而特别令人感兴趣。此外，该亚种的缺陷最近与人类几种类型的纤毛病有关，例如原发性纤毛运动障碍和鞭毛的多种形态异常。在这篇小综述中，我们讨论了在模式生物莱茵衣藻中研究的 IDA d 的组成、结构和运动特性，并进一步讨论了 IDA d 与人类纤毛病之间的关系。此外，我们提供了未来的观点并讨论了有关这个有趣的动力蛋白亚种的剩余问题。