ABSTRACT
This chapter describes the molecular compositions and the regulatory mechanism of axonemal dynein. It explores the molecular composition of axonemal dynein and the regulatory mechanisms of ciliary and flagellar motility. Axonemal dyneins are divided into two classes: outer-arm dyneins and inner-arm dyneins. Sperm flagella have been the sources for studying axonemal dyneins. The axonemal dyneins have been isolated from sperm of several animals, but those isolated from sea urchins and tunicates have been most widely studied. The outer-arm dynein from the ascidian Ciona intestinalis contains additional two or three intermediate chains (IC), termed IC4 and IC5. The activity of outer-arm dynein in sperm flagella is regulated by phosphorylation of the subunits, such as the Tctex2-related light chain. Inner-arm dyneins are structurally and functionally more diverse than outer-arm dynein. Structure and subunit composition of the inner-arm dynein has been less studied in metazoan species.
