Dabauvalle M C, Franke W W
Exp Cell Res. 1984 Aug;153(2):308-26. doi: 10.1016/0014-4827(84)90603-7.
The cytoplasm of oocytes of Xenopus laevis is enriched in several soluble proteins which are either absent from the nucleus or are present there at very low concentrations. These molecules, collectively referred to as karyophobic (from the Greek verbs and which are meant here in the sense of "to be afraid of" or "to avoid") proteins represent more than 20% of the total soluble cytoplasmic proteins and include some of the most abundant soluble cellular components. They may be recovered from high-speed supernatant (S-100) fractions and, following sucrose gradient centrifugation, most of them appear in the form of complexes smaller than 8.5 S. On denaturation in urea and two-dimensional gel electrophoresis these proteins appear to be comprised of polypeptides of widely different sizes (ca Mr 15 000-230 000) and isoelectric points covering a broad range of pH values (4.2-8.0). Gel filtration and isoelectric focusing of native karyophobic proteins show that the majority occur in acidic complexes smaller than Mr 150 000, including one case of a small karyophobic protein (C9; Mr 30 000). In contrast to karyophilic proteins and proteins equilibrating between nucleus and cytoplasm karyophobic soluble proteins from [35S]methionine-labelled ooplasms, when injected into unlabelled oocytes, remain in the cytoplasm. Human proteins with a similar karyophobic behaviour have been identified in fractions of soluble proteins from HeLa cells; there, the major karyophobic protein (HCa Mr 36 000) is also one of the most abundant soluble proteins. We conclude that the specific nucleocytoplasmic compartmentalization of soluble proteins is governed not only by the principles of exclusion of large molecules from nuclear uptake and the existence of karyophilic signals in certain proteins but that a series of soluble, globular proteins exist in the cytoplasm, which have other molecular features which selectively exclude them from distribution over the nucleus. The possible functional role of the selective enrichment of these abundant proteins, which so far have escaped attention, in establishing a cytoplasmic milieu is discussed.
非洲爪蟾卵母细胞的细胞质富含几种可溶性蛋白质，这些蛋白质要么在细胞核中不存在，要么在细胞核中的浓度非常低。这些分子统称为核排斥蛋白（源自希腊动词，这里的意思是“害怕”或“避免”），占可溶性细胞质蛋白总量的20%以上，包括一些最丰富的可溶性细胞成分。它们可以从高速上清液（S-100）组分中回收，经过蔗糖梯度离心后，大多数以小于8.5 S的复合物形式出现。在尿素中变性并进行二维凝胶电泳后，这些蛋白质似乎由大小差异很大（约Mr 15 000-230 000）且等电点覆盖广泛pH值范围（4.2-8.0）的多肽组成。天然核排斥蛋白的凝胶过滤和等电聚焦表明，大多数存在于小于Mr 150 000的酸性复合物中，包括一种小的核排斥蛋白（C9；Mr 30 000）。与亲核蛋白和在细胞核与细胞质之间平衡的蛋白质不同，来自[35S]甲硫氨酸标记的卵质的核排斥可溶性蛋白质，当注射到未标记的卵母细胞中时，仍留在细胞质中。在来自HeLa细胞的可溶性蛋白质组分中已鉴定出具有类似核排斥行为的人类蛋白质；在那里，主要的核排斥蛋白（HCa Mr 36 000）也是最丰富的可溶性蛋白质之一。我们得出结论，可溶性蛋白质的特定核质区室化不仅受大分子被排除在核摄取之外的原则以及某些蛋白质中亲核信号的存在的控制，而且细胞质中存在一系列可溶性球状蛋白质，它们具有其他分子特征，可选择性地将它们排除在细胞核的分布之外。讨论了这些迄今为止未被关注的丰富蛋白质的选择性富集在建立细胞质环境中可能的功能作用。
