STRUCTURE AND FUNCTION OF CYTOPLASMIC MOTORS

本项目的目标是了解它们的分布和功能 神经元轴突中的细胞质马达。此信息是 旨在导致在分子水平上对FAST的理解 和缓慢的轴突运输以及细胞质的组织 轴突。我们的结果表明，激动素更紧密地与 细胞器表面比动力蛋白导致了简单的阐述 运输方向取决于顺行囊泡结合的观点 动蛋白和逆行小泡结合动力蛋白。因为细胞器 可以在向下运输的过程中保留其特定的肌动蛋白 轴突，我们认为激动素的上调或下调决定了 运输的方向。新型肌球蛋白马达已经被 发现附着在鱿鱼轴突细胞器的表面，它 现在看来，至少有两种肌球蛋白也参与其中 在细胞器运输中。我们已经研制出了针对这两种病毒的抗体 肌球蛋白，这两种肌球蛋白都与细胞器相关。新研究 轴突中这些马达的肌动蛋白底物的组织 已经表明平行的肌动蛋白细丝与微管缠绕在一起 它们具有混合的极性，这表明它们可能 将细胞器运送到微管束和从微管束传出。我们做了一个 从定义慢速运输的机制开始。带负电荷 注入鱿鱼巨型轴突的大分子集合体在 顺行方向，速度高达0.5微米/秒。特别感兴趣的 神经丝蛋白以及肌动蛋白和微管 碎片是顺行移动的，而且所有的移动似乎都是沿着 某种类型的细胞内束。这项体外试验应该会成功 有可能定义这种运动的马达。细菌 大肠杆菌中的鞭毛马达被研究为另一个例子 电机系统可以切换变位方向。我们是 完成对这一细胞质表达的结构研究 马达预计将提供有关

The goal of this project is to understand the distribution and functions of cytoplasmic motors in the axon of neurons. This information is intended to lead to an understanding, at the molecular level, of fast and slow axonal transport as well as the cytoplasmic organization in the axon. Our results showing that kinesin is more tightly bound to organelle surfaces than dynein have led to elaboration of the simple idea that direction of transport depends on anterograde vesicles binding kinesin and retrograde vesicles binding dynein. Since an organelle could retain its particular kinesins while it is being transported down the axon, we propose that up or down regulation of kinesin determines the direction of transport. New types of myosin motors has been discovered attached to the surfaces of squid axonal organelles, and it now appears that there are at least two species of myosin also involved in organelle transport. We have developed antibodies to both of these myosins, and both myosins are associated with organelles. New studies of the organization of the actin substrates for these motors in the axon has showed that parallel actin filaments intertwine with the microtubule bundles, and that they have mixed polarities, suggesting that they might carry organelles both to and from the microtubule bundles. We made a start on defining the mechanism of slow transport. Negatively charged macromolecule assemblies injected into the squid giant axon move in the anterograde direction at rates up to 0.5 um/sec. Of particular interest is that neurofilament proteins as well as actin and microtubule fragments move anterogradely, and that all movements appear to be along some type of intracellular tract. This in vitro assay should make it possible to define the motors for such movements. The bacterial flagellar motor in E. coli has been studied as another example of a motor system than can switch direction of translocation. We are completing a structural study of the cytoplasmic representation of this motor which is expected to provide new information on the