STRUCTURE AND FUNCTION OF CYTOPLASMIC MOTORS

本项目的目标是了解分布和功能 神经元轴突中的细胞质马达。 该信息 目的是在分子水平上理解快速和 缓慢的轴突运输以及细胞质组织在 轴突 这是该科的中心项目， 这一年，我们收获了很多新的发现。 一种新型 鱿鱼轴突表面肌球蛋白II样马达亚类 细胞器已被发现，这种肌球蛋白及其钙调蛋白- 现在可以从大脑中大量纯化类似的轻链， 表征了免疫标记显示，这种肌球蛋白强烈粘附于 轴突细胞器的表面。 行动组织 轴突中这些马达的底物表明，肌动蛋白丝 与微管束交错。 一种可用于以下的测定： 探讨了界定慢化机制的难题， 还引进了交通工具。注入的大分子组装体 进入鱿鱼的巨大轴突正以一定的速度 高达0.5毫米/秒。 特别令人感兴趣的是短肌动蛋白丝 也是顺行的，所有的运动似乎都是沿着一些 胞内束的类型。这个体外试验应该可以 以定义用于这种运动的马达。 细菌鞭毛马达 在大肠大肠杆菌作为运动系统的另一个例子， 转换易位方向。一种新的细胞质成分， 鞭毛马达被认为与方向转换有关， 已经被分离和纯化，我们正在设计一种 这是一个结构模型，说明马达中的蛋白质是如何 有组织的。

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. This is the central project in the Section, and has been very productive this year, providing a plethora of new findings. A novel subclass of myosin II-like motors on the surfaces of squid axonal organelles has been discovered and this myosin as well as its calmodulin- like light chain can now be purified in quantity from brain, and is being characterized. Immunolabeling shows that this myosin adheres strongly to the surfaces of axonal organelles. The organization of the actin substrates for these motors in the axon has showed that actin filaments intertwine with the microtubule bundles. An assay that may be useful for approaching the difficult problem of defining the mechanism of slow transport has also been introduced. Macro-molecular assemblies injected into the squid giant axon are move in the anterograde direction at rates up to 0.5 Mm/sec. Of particular interest is that short actin filaments also 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. A new cytoplasmic component of the flagellar motor thought to be involved in directional switching has now been isolated and purified, and we are making progress in devising a structural model of how the proteins in this component of the motor are organized.