The mechanism regulating the activity of oscillatory motor protein, dynein

鞭毛运动的一个显著特征是摆动。鞭毛的振荡运动是基于动力蛋白的活性，动力蛋白是微管运动蛋白之一。本研究旨在阐明鞭毛轴丝中动力蛋白活性的调控机制。我们使用了海胆精子鞭毛，将其去膜、碎裂，然后用弹性蛋白酶处理。应用1 mM三磷酸腺苷诱导经弹性酶处理的轴丝滑动成两组双胞体，其中一组包含中央对。当用几种荧光ATP代替ATP时，我们发现动力蛋白对它们没有引起滑动的作用。在第二个实验中，我们发现，在有ATP存在的情况下，在含有内臂和5%外臂的轴丝中加入350 kDa的外臂胰酶片段，可以显著提高ATP诱导的轴丝滑动速度。由于这些片段的ATPase活性高于外臂，动力蛋白臂之间的活性可能是通过双重微管来调节的。在第三个实验中，通过单线微管与暴露在双线组上的动力蛋白臂相互作用和分裂轴丝的超微结构分析，研究了中心对对动力蛋白活性的影响。我们发现，钙通过涉及中心对和径向辐条复合体的调节机制来抑制二联体上动力蛋白臂的活动。这一机制可能控制轴丝内动力蛋白活性的转换，从而诱导鞭毛的振荡弯曲运动。

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.