Stearns T, Kirschner M
Department of Biochemistry and Biophysics, University of California Medical School, San Francisco 94143.
Cell. 1994 Feb 25;76(4):623-37. doi: 10.1016/0092-8674(94)90503-7.
The centrosome nucleates microtubule polymerization, affecting microtubule number, polarity, and structure. We use an in vitro system based on extracts of Xenopus eggs to examine the role of gamma-tubulin in centrosome assembly and function. gamma-Tubulin is present in the cytoplasm of frog eggs and vertebrate somatic cells in a large approximately 25S complex. The egg extracts assemble centrosomes around sperm centrioles. Formation of a centrosome in the extract requires both the gamma-tubulin complex and ATP and can take place in the absence of microtubules. gamma-Tubulin is not present on the sperm prior to incubation in extract, but is recruited from the cytoplasm during centrosome assembly. The gamma-tubulin complex also binds to microtubules, likely the minus end, independent of the centrosome. These results suggest that gamma-tubulin is an essential component of the link between the centrosome and the microtubule, probably playing a direct role in microtubule nucleation.
中心体介导微管聚合，影响微管数量、极性和结构。我们使用基于非洲爪蟾卵提取物的体外系统来研究γ-微管蛋白在中心体组装和功能中的作用。γ-微管蛋白以大约25S的大复合物形式存在于蛙卵和脊椎动物体细胞的细胞质中。卵提取物围绕精子中心粒组装中心体。提取物中中心体的形成需要γ-微管蛋白复合物和ATP，并且可以在没有微管的情况下发生。在提取物中孵育之前，精子上不存在γ-微管蛋白，但在中心体组装过程中从细胞质中募集而来。γ-微管蛋白复合物也与微管结合，可能是与负端结合，且与中心体无关。这些结果表明，γ-微管蛋白是中心体与微管之间联系的重要组成部分，可能在微管成核中起直接作用。
