The mechanism regulating the activity of dynein, an oscillatory motor protein.

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A prominent feature of flagellar motility is an oscillation. Flagellar oscillatory movement is based on the activity of dynein, which is one of the microtubule motor proteins. In this study I aimed to elucidate the mechanism regulating the dynein activity in the flagellar axonemes. I used sea urchin sperm flagella, which were demembranated, fragmented and then treated with elastase. A flash photolysis of caged ATP induced sliding of the elastase-treated axonemes into two groups of doublets, one of them contained the central pair. I investigated an effect of bending a part of these doublet groups and found that the bending induced two characteristic changes. One was an increase in the velocity of sliding between the two groups of the doublets. Another change was a sliding pattern, that is, the sliding occurred between any two of the nine doublets. These results indicate that the microtubule bending is involved in the regulation of dynein activity. In the second experiment, an effect of the central pair on dynein activity was studied by using singlet microtubules, which interacted with exposed dynein arms on doublets of the doublet groups. I found that the presence of the central pair inhibited the sliding activity of dynein at high calcium conditions. In the third experiment, effects of mechanical perturbation on the oscillatory force of a single dynein arm was measured and the oscillatory force was reveled to be changed by the mechanical changes applied to the doublet or the microtubules.