Collins L, Tsien W H, Seals C, Hakimi J, Weber D, Bailon P, Hoskings J, Greene W C, Toome V, Ju G
Department of Molecular Genetics, Hoffmann-La Roche Inc., Nutley, NJ 07110.
Proc Natl Acad Sci U S A. 1988 Oct;85(20):7709-13. doi: 10.1073/pnas.85.20.7709.
Analogs of interleukin 2 containing defined amino acid substitutions and deletions were assayed for bioactivity and for competitive binding to the high-affinity human interleukin 2 receptor complex and its two component subunits, a 55-kDa subunit (p55 or TAC) and a 70-kDa subunit (p70). Substitution of Asp20 or deletion of Phe124 resulted in inactive analog proteins that were unable to interact with the high-affinity p55/p70 complex or the intermediate-affinity p70 subunit of the interleukin 2 receptor. These analogs, however, retained the capacity to compete for binding to the low-affinity p55 subunit. The presence of the carboxylic acid in the side chain of Asp20 was necessary for effective binding to the p70 protein. In contrast, substitution of Trp121 and Leu17 created analogs that were inactive in the bioassay and all three binding assays. The effects of these mutations on protein conformation were assessed by circular dichroism. These results demonstrate that specific residues in the NH2 and COOH termini of interleukin 2 are crucial for its structure and activity.
对含有特定氨基酸取代和缺失的白细胞介素2类似物进行了生物活性测定，以及与高亲和力人白细胞介素2受体复合物及其两个组成亚基（一个55 kDa亚基（p55或TAC）和一个70 kDa亚基（p70））的竞争性结合测定。天冬氨酸20被取代或苯丙氨酸124缺失导致无活性的类似物蛋白，其无法与白细胞介素2受体的高亲和力p55/p70复合物或中等亲和力p70亚基相互作用。然而，这些类似物保留了与低亲和力p55亚基竞争结合的能力。天冬氨酸20侧链中的羧酸的存在对于有效结合p70蛋白是必需的。相比之下，色氨酸121和亮氨酸17被取代产生的类似物在生物测定和所有三种结合测定中均无活性。通过圆二色性评估了这些突变对蛋白质构象的影响。这些结果表明，白细胞介素2的NH2和COOH末端的特定残基对其结构和活性至关重要。
