The mechanism regulating the activity of oscillatory motor protein, dynein

点击翻译按钮获取中文摘要

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 we aimed to elucidate the mechanism regulating the dynein activity in the flagellar axonemes. We used sea urchin sperm flagella, which were demembranated, fragmented and then treated with elastase. An application of 1 mM ATP induced sliding of the elastase-treated axonemes into two groups of doublets, one of them contained the central pair. When several kinds of fluorescent ATP were used instead of ATP, we found that the dynein hydrolysed them without inducing the sliding. In the second experiment, we found that the velocity of sliding induced by ATP in the elastase-treated axonemes, which had the inner arms and 5% of the outer arms, was significantly increased by adding 350 kDa trypsin-fragments of the outer arms to the axonemes in the presence of ATP. Because the ATPase activity of the fragments was higher than that of the outer arms, the activity between dynein arms might be regulated through the doublet microtubules. In the third experiment, the 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 and ultrastructural analysis of split axonemes. We found that calcium inhibits the activity of dynein arms on the doublets through the regulatory mechanism that involves the central pair and the radial spoke complex. This mechanism might control the switching of the dynein activity within the axoneme to induce the oscillatory bending movement of the flagellum.