Martin O C, Gunawardane R N, Iwamatsu A, Zheng Y
Department of Embryology, Carnegie Institution of Washington, Baltimore, Maryland 21210, USA.
J Cell Biol. 1998 May 4;141(3):675-87. doi: 10.1083/jcb.141.3.675.
Previous studies indicate that gamma tubulin ring complex (gammaTuRC) can nucleate microtubule assembly and may be important in centrosome formation. gammaTuRC contains approximately eight subunits, which we refer to as Xenopus gamma ring proteins (Xgrips), in addition to gamma tubulin. We found that one gammaTuRC subunit, Xgrip109, is a highly conserved protein, with homologues present in yeast, rice, flies, zebrafish, mice, and humans. The yeast Xgrip109 homologue, Spc98, is a spindle-pole body component that interacts with gamma tubulin. In vertebrates, Xgrip109 identifies two families of related proteins. Xgrip109 and Spc98 have more homology to one family than the other. We show that Xgrip109 is a centrosomal protein that directly interacts with gamma tubulin. We have developed a complementation assay for centrosome formation using demembranated Xenopus sperm and Xenopus egg extract. Using this assay, we show that Xgrip109 is necessary for the reassembly of salt-disrupted gammaTuRC and for the recruitment of gamma tubulin to the centrosome. Xgrip109, therefore, is essential for the formation of a functional centrosome.
先前的研究表明，γ微管蛋白环复合物（γTuRC）能够促使微管组装成核，并且在中心体形成过程中可能发挥重要作用。γTuRC除了含有γ微管蛋白外，还包含大约八个亚基，我们将其称为非洲爪蟾γ环蛋白（Xgrips）。我们发现，γTuRC的一个亚基Xgrip109是一种高度保守的蛋白质，在酵母、水稻、果蝇、斑马鱼、小鼠和人类中均存在同源物。酵母中的Xgrip109同源物Spc98是一种与γ微管蛋白相互作用的纺锤极体成分。在脊椎动物中，Xgrip109识别出两个相关蛋白家族。Xgrip109和Spc98与其中一个家族的同源性高于另一个家族。我们发现Xgrip109是一种中心体蛋白，可直接与γ微管蛋白相互作用。我们利用去膜的非洲爪蟾精子和非洲爪蟾卵提取物开发了一种用于中心体形成的互补分析方法。通过该分析方法，我们发现Xgrip109对于盐破坏的γTuRC的重新组装以及γ微管蛋白向中心体的募集是必需的。因此，Xgrip109对于功能性中心体的形成至关重要。
