Kleinschmidt J A, Franke W W
Cell. 1982 Jul;29(3):799-809. doi: 10.1016/0092-8674(82)90442-1.
Oocyte nuclei of Xenopus laevis contain nucleosomal-core histones in large amounts and in a soluble, non-chromatin-bound form. Supernatant fractions (100,000 X g) from isolated nuclei are enriched in complexes containing histones H3 and H4, which are of distinct size (5.6S by sucrose gradient centrifugation, approximate molecular weight of 270,000 by gel filtration) and negatively charged (isoelectric at pH 4.4). These complexes bind to DEAE-Sephacel and can be separated from nucleoplasmin. In diverse fractionation experiments, histones H3 and H4 have been found to comigrate with a pair of polypeptides of molecular weight 110,000 that represent the most acidic major protein present in these nuclei. After enrichment by gel filtration, ion exchange chromatography and electrophoresis, this pair of acidic polypeptides has been the only nonhistone protein detected in the histone-complex fraction. We suggest that in the oocyte nucleus, large proportions of the soluble histones H3 and H4 are not contained in complexes of all four nucleosomal-core histones but are differentially associated with specific, very acidic proteins into distinct 5.6S complexes.
非洲爪蟾的卵母细胞核含有大量呈可溶、非染色质结合形式的核小体核心组蛋白。分离细胞核得到的上清液组分（100,000×g）富含包含组蛋白H3和H4的复合物，这些复合物大小各异（通过蔗糖梯度离心为5.6S，通过凝胶过滤法测得近似分子量为270,000）且带负电荷（在pH 4.4时呈等电状态）。这些复合物能与二乙氨基乙基纤维素（DEAE - Sephacel）结合，并且可以与核质蛋白分离。在各种分级分离实验中，已发现组蛋白H3和H4与一对分子量为110,000的多肽一同迁移，这对多肽代表了这些细胞核中存在的最酸性的主要蛋白质。经过凝胶过滤、离子交换色谱和电泳富集后，这对酸性多肽是在组蛋白复合物组分中检测到的唯一非组蛋白。我们认为，在卵母细胞核中，大部分可溶的组蛋白H3和H4并非包含在所有四种核小体核心组蛋白的复合物中，而是与特定的、非常酸性的蛋白质以不同方式结合形成独特的5.6S复合物。
