Liu F T, Orida N
J Biol Chem. 1984 Sep 10;259(17):10649-52.
Immunoglobulin E-binding activity was expressed in Xenopus oocytes injected with mRNA from rat basophilic leukemia cells which possess abundant immunoglobulin E (IgE) receptor. Such activity was demonstrated with intact oocytes by their binding of 125I-labeled mouse monoclonal IgE. Binding activity was specific as shown by the total inhibition of 125I-IgE binding by unlabeled IgE but not by unlabeled IgG1. The relevance of the IgE-binding activity to the IgE receptor was also supported by the absence of this activity in oocytes injected with mRNA from cells lacking surface IgE receptors. mRNA coding for the IgE-binding activity was enriched in fractions sedimenting at 13.5 S in sucrose density gradients. From oocytes injected with rat basophilic leukemia mRNA, two major polypeptides were isolated by affinity purification on IgE immunoadsorbent. One (Mr = 31,000) is equivalent in size to the previously identified "receptor-associated protein;" the other (Mr = 40,000) is speculated to be a partially glycosylated or unglycosylated form of the alpha subunit of the IgE receptor. The binding of IgE-coated fluorescent microspheres by oocytes injected with rat basophilic leukemia mRNA demonstrated the surface expression of the IgE-binding proteins.
将来自具有丰富免疫球蛋白E（IgE）受体的大鼠嗜碱性白血病细胞的mRNA注射到非洲爪蟾卵母细胞中后，可表达免疫球蛋白E结合活性。完整的卵母细胞通过结合125I标记的小鼠单克隆IgE来证明这种活性。未标记的IgE可完全抑制125I-IgE的结合，而未标记的IgG1则不能，这表明结合活性具有特异性。在注射了缺乏表面IgE受体的细胞的mRNA的卵母细胞中不存在这种活性，这也支持了IgE结合活性与IgE受体的相关性。编码IgE结合活性的mRNA在蔗糖密度梯度中以13.5 S沉降的级分中富集。从注射了大鼠嗜碱性白血病mRNA的卵母细胞中，通过IgE免疫吸附剂亲和纯化分离出两种主要多肽。一种（Mr = 31,000）的大小与先前鉴定的“受体相关蛋白”相当；另一种（Mr = 40,000）推测是IgE受体α亚基的部分糖基化或未糖基化形式。注射了大鼠嗜碱性白血病mRNA的卵母细胞对IgE包被的荧光微球的结合证明了IgE结合蛋白的表面表达。
