Lessman C A, Kim H
Department of Microbiology and Molecular Cell Sciences, The University of Memphis, Memphis, Tennessee 38152-6041, USA.
Mol Reprod Dev. 2001 Sep;60(1):128-36. doi: 10.1002/mrd.1069.
Oocytes of the leopard frog, Rana pipiens, contain soluble tubulin which was previously shown to exist predominantly in megadalton (MDa) fractions and that fails to readily assemble in vitro. In order to further characterize these tubulin complexes, DEAE Sepharose chromatography, Sephacryl S-300 size exclusion columns and specific immunoprecipitation were used. The results revealed the presence of alpha-, beta-, and gamma-tubulin associated with several other proteins in the soluble fraction of Rana pipiens ovarian oocytes. These Rana oocyte tubulin complexes appear to be analogous to those recently reported in Xenopus ovulated eggs as gamma-tubulin ring complexes. This seems true since both size (estimates, i.e. approximately 2MDa) and protein components are similar. Furthermore, both alpha- and gamma-tubulin antibodies immunoprecipitated identical protein bands from Rana oocyte soluble fraction. These putative Rana gamma-tubulin ring proteins include 107, 97, 95, 90 and 75 kDa components which are similar in size to those found in Xenopus and other species. Rana appears to belong to a select group in which gamma-tubulin complexes contain significant alpha- and beta-tubulin (i.e., Xenopus and sheep), while other species such as Drosophila, Aspergillus, Saccharomyces, human cells and many other mammalian cells tested lack the other tubulin components. The heterogeneity in both size and protein components of Rana oocyte gamma-tubulin ring complexes may reflect different states of tubulin complex assembly. The lower vertebrate oocyte is hypothesized to act as a repository and prestaging point for the assembly of gamma-tubulin ring complexes which will become the maternal contribution to the centrosomes of the embryo. While the gamma-tubulin ring complexes of vertebrate eggs have been described previously, this is the first report biochemically characterizing soluble gamma-tubulin complexes in vertebrate ovarian oocytes.
豹蛙（北美林蛙）的卵母细胞含有可溶性微管蛋白，此前研究表明，这种微管蛋白主要存在于兆道尔顿（MDa）级分中，且在体外不易组装。为了进一步表征这些微管蛋白复合物，采用了二乙氨基乙基琼脂糖凝胶色谱法、Sephacryl S - 300尺寸排阻柱和特异性免疫沉淀法。结果显示，在豹蛙卵巢卵母细胞的可溶性级分中，α -、β - 和γ - 微管蛋白与其他几种蛋白质相关联。这些豹蛙卵母细胞微管蛋白复合物似乎类似于最近在非洲爪蟾排卵卵中报道的γ - 微管蛋白环复合物。这似乎是成立的，因为两者的大小（估计约为2MDa）和蛋白质成分相似。此外，α - 和γ - 微管蛋白抗体从豹蛙卵母细胞可溶性级分中免疫沉淀出相同的蛋白条带。这些假定的豹蛙γ - 微管蛋白环蛋白包括107、97、95、90和75 kDa的成分，其大小与在非洲爪蟾和其他物种中发现的相似。豹蛙似乎属于一个特定的群体，其中γ - 微管蛋白复合物含有大量的α - 和β - 微管蛋白（即非洲爪蟾和绵羊），而其他物种，如果蝇、曲霉属、酿酒酵母、人类细胞以及许多其他测试过的哺乳动物细胞，则缺乏其他微管蛋白成分。豹蛙卵母细胞γ - 微管蛋白环复合物在大小和蛋白质成分上的异质性可能反映了微管蛋白复合物组装的不同状态。据推测，低等脊椎动物的卵母细胞充当γ - 微管蛋白环复合物组装的储存库和预阶段点，这些复合物将成为胚胎中心体的母体贡献。虽然脊椎动物卵的γ - 微管蛋白环复合物此前已有描述，但这是第一份对脊椎动物卵巢卵母细胞中可溶性γ - 微管蛋白复合物进行生化表征的报告。
