The molecular motors of cilia and eukaryotic flagella.

Axonemal dyneins occur in two rows (as inner and outer arms) on each of the nine doublets. Axonemal dynein binds reversibly to the B-microtubule and has an ATP-insensitive anchorage to the A-microtubule of the adjacent doublet. The heavy chains have the form of globular heads and are responsible for chemo-mechanical transduction. The B-tubule-binding site is on a tenuous extension of the head. There is only one type of ODA. A 12 nm shift in the globular heads is associated with the hydrolysis cycle. There are three types of IDA. No functional changes have been recognized in their complex conformation. There is plentiful evidence that the axonemal dyneins produce interdoublet displacement. Doubt remains on how much sliding occurs per cycle of ATP hydrolysis. The mechanism for transforming sliding into bending is not yet explained.