Malek T R, Korty P E
J Immunol. 1986 Jun 1;136(11):4092-8.
The IL 2 receptor isolated from the IL 2-dependent CTL-L cell line was subjected to biochemical analysis. Pulse-chase and tunicamycin studies, as well as digestion with the endoglycosidases, Endo-F and Endo-H, of 35S-methionine-labeled IL 2 receptors suggested a single protein precursor of 32,000 (p32) daltons. The p32 precursor was rapidly processed by addition of high-mannose-containing core N-linked sugars to intracytoplasmic precursor intermediates of 38,000 (p38) and 40,000 (p40) daltons, which undergo further processing to yield a mature surface receptor with heterogeneous apparent m.w. of 52,000 to 65,000 (p58). Two-dimensional gel studies indicated that p58 exhibited broad charge heterogeneity between pH 4.6 and 6.3. Endo-F digestions of p58 shifted the isoelectric focus point to a more basic 5.5 to 7.4. This considerable charge heterogeneity is consistent with the possibility that other posttranslational modifications to the mouse IL 2 receptor occur besides addition of complex N-linked glycans. Immunoprecipitations of the IL 2 receptor from surface iodinated cells also revealed an additional band at 110,000 (p110) daltons. IEF vs SDS-PAGE two-dimensional gel studies demonstrated that p110 also had an isoelectric focus point identical to p58. Western blot studies with an anti-IL 2 receptor monoclonal antibody (7D4) demonstrated that p38, p40, p58, and p110 each expressed the epitope recognized by this antibody. Thus, it is likely that p110 is not a unique molecule that coprecipitates with the IL 2 receptor. Western blot analysis of mitogen-stimulated T and B lymphocytes also revealed bands similar to p58 and p110, although these bands had an average apparent m.w. 3000 to 6000 less than those seen for CTL-L cells.
从依赖白细胞介素2（IL-2）的CTL-L细胞系中分离出的IL-2受体进行了生化分析。脉冲追踪和衣霉素研究，以及用内切糖苷酶Endo-F和Endo-H对35S-甲硫氨酸标记的IL-2受体进行消化，表明存在一种32,000（p32）道尔顿的单一蛋白质前体。通过向38,000（p38）和40,000（p40）道尔顿的胞质前体中间体添加含高甘露糖的核心N-连接糖，p32前体被快速加工，这些中间体进一步加工产生成熟的表面受体，其表观分子量异质性为52,000至65,000（p58）。二维凝胶研究表明，p58在pH 4.6至6.3之间表现出广泛的电荷异质性。p58的Endo-F消化将等电聚焦点转移到更碱性的5.5至7.4。这种相当大的电荷异质性与除了添加复杂的N-连接聚糖之外，小鼠IL-2受体还发生其他翻译后修饰的可能性一致。从表面碘化细胞中免疫沉淀IL-2受体还揭示了一条位于110,000（p110）道尔顿的额外条带。IEF与SDS-PAGE二维凝胶研究表明，p110的等电聚焦点也与p58相同。用抗IL-2受体单克隆抗体（7D4）进行的蛋白质印迹研究表明，p38、p40、p58和p110均表达该抗体识别的表位。因此，p110可能不是与IL-2受体共沉淀的独特分子。对有丝分裂原刺激的T和B淋巴细胞进行的蛋白质印迹分析也揭示了与p58和p110相似的条带，尽管这些条带的平均表观分子量比CTL-L细胞中的条带小3000至6000。
