STRUCTURE AND ASSEMBLY OF CYTOSKELETAL FILAMENTS

细胞骨架领域最令人兴奋的最新进展之一 是发现FtsZ，一种细菌细胞分裂蛋白， 微管蛋白同系物。 同源性首先通过其GT3来表示 活动，然后通过FtsZ和所有 微管蛋白 两个实验室最近证明，FtsZ可以形成 聚合物，但它们与微管的结构关系尚不清楚。 我们 实验室现在已经证明FtsA可以转化为原丝， 片和环与聚合物惊人地相似， 真核微管蛋白 FtsZ似乎是主要的细菌细胞骨架蛋白，形成了一个细胞骨架。 （收缩性？）在分隔部位形成环状。 我们计算了一下， 每个细胞的FtsZ分子足以形成单个原丝 环绕细菌23次，足以形成一个 反平行细丝的可收缩环。 的生理聚合物 FtsZ仍然未知，但可能是一小片或一束 原丝 我们研究的第一个目标是确定 聚合物在不同的溶液条件下形成，使用负染色和 旋转阴影电子显微术 从这一点，我们希望推断出 可能在分隔沟处起作用的结构。 我们 特别感兴趣的是GTP如何用于FtsZ的聚合， 在微管组装和动力学不稳定性方面与GTdR进行比较。 我们建议从其他几种细菌中克隆FtsZ， 特别是固氮菌，它可能有一个[原核微管- 微管进化中缺失的一环 我们还建议寻找 一种小鼠线粒体FtsZ，基于最近的发现， 拟南芥叶绿体FtsZ。 我们计划研究 叶绿体FtsZ与Osteryoung博士合作，Osteryoung博士克隆了它， 并希望最终能够描述小鼠线粒体的聚合物 FtsZ。 叶绿体和线粒体FtsZ可能参与了线粒体的分裂。 这些细胞器。 FtsZ为X射线晶体学提供了极好的前景，并可能提供 解决了几个阻碍晶体学发展的问题 真核细胞微管蛋白。 因为它们是同源蛋白质， FtsZ的结构也将提供微管蛋白的大部分结构。 已知几种细菌蛋白与FtsZ相互作用， 其他人必须存在。 我们对苏拉特别感兴趣， FtsA的功能和可能是B单体结合或加帽蛋白。 锚 穿过内膜并可使聚合物组装成核的蛋白质 将被寻求。 最后，我们相信，与 FtsZ很可能存在，这是寻找原核同源物的一个建议 驱动蛋白或动力蛋白。

One of the most exciting recent developments in the field of cytoskeleton is the discovery that FtsZ, a bacterial cell division protein, is a homologue of tubulin. The homology was first indicated by its GTPase activity, then by very compelling sequence identities between FtsZ and all tubulins. Two laboratories recently demonstrated that FtsZ could form polymers, but their structural relation to microtubules was not clear. Our lab has now demonstrated that FtsA will polymerize into protofilaments, sheets an rings that are strikingly similar to polymers formed by eukaryotic tubulins. FtsZ appears to be the major bacterial cytoskeletal protein, forming a (contractile?) ring at the site of septation. We calculate that the 10,000 molecules of FtsZ per cell are sufficient to make a single protofilament that encircles the bacterium 23 times, more than sufficient to form a contractile ring of anti-parallel filaments. The physiological polymer of FtsZ is still not known, but may be a small sheet or bundle of protofilaments. The first goal of our studies is to determine the range of polymer forms in different solution conditions, using negative stain and rotary shadowing electron microscopy. From this we hope to deduce the structures that are likely to operate at the septation furrow. We are especially interested in how GTP is utilized in the polymerization of FtsZ, to compare with the GTPase in microtubule assembly and dynamic instability. We propose to clone FtsZ from several other bacterial species, in particular Azotobacter, which may have a [prokaryotic microtubule - the missing link in evolution of microtubules. We also propose to search for a mouse mitochondrial FtsZ, based on the very recent discovery of chloroplast FtsZ in Arabidopsis. We plan to study the polymers of the chloroplast FtsZ in collaboration with Dr. Osteryoung, who has cloned it, and eventually hope to characterize the polymers of mouse mitochondrial FtsZ. Chloroplast and mitochondrial FtsZ may be involved in division of these organelles. FtsZ offers excellent prospects for x-ray crystallography, and may provide solutions to the several problems that have prevented any crystallography of eukaryotic tubulins. Because they are homologous proteins, an atomic structure of FtsZ will also provide most of the structure of tubulin. Several bacterial proteins are already known that interact with FtsZ, and others must exist. We are particularly interested in SulA, which blocks FtsA function and may b e monomer-binding or a capping protein. Anchor proteins that traverse the inner membrane and may nucleate polymer assembly will be sought. Finally, we believe that motor proteins interacting with FtsZ are likely to exist, an propose to search for prokaryotic homologues of kinesin or dynein.