Sauvé K, Nachman M, Spence C, Bailon P, Campbell E, Tsien W H, Kondas J A, Hakimi J, Ju G
Department of Molecular Genetics, Roche Research Center, Hoffmann-La Roche Inc., Nutley, NJ 07110.
Proc Natl Acad Sci U S A. 1991 Jun 1;88(11):4636-40. doi: 10.1073/pnas.88.11.4636.
Human interleukin 2 (IL-2) analogs with defined amino acid substitutions were used to identify specific residues that interact with the 55-kDa subunit (p55) or alpha chain of the human IL-2 receptor. Analog proteins containing specific substitutions for Lys-35, Arg-38, Phe-42, or Lys-43 were inactive in competitive binding assays for p55. All of these analogs retained substantial competitive binding to the intermediate-affinity p70 subunit (beta chain) of the receptor complex. The analogs varied in ability to interact with the high-affinity p55/p70 receptor. Despite the lack of binding to p55, all analogs exhibited significant biological activity, as assayed on the murine CTLL cell line. The dissociation constants of Arg-38 and Phe-42 analogs for p70 were consistent with intermediate-affinity binding; the Kd values were not significantly affected by the presence of p55 in binding to the high-affinity IL-2 receptor complex. These results confirm the importance of the B alpha-helix in IL-2 as the locus for p55-receptor binding and support a revised model of IL-2-IL-2 receptor interaction.
具有特定氨基酸取代的人白细胞介素2（IL-2）类似物被用于鉴定与人类IL-2受体的55 kDa亚基（p55）或α链相互作用的特定残基。含有赖氨酸-35、精氨酸-38、苯丙氨酸-42或赖氨酸-43特定取代的类似蛋白在p55的竞争性结合试验中无活性。所有这些类似物对受体复合物的中等亲和力p70亚基（β链）仍保持大量竞争性结合。这些类似物与高亲和力p55/p70受体相互作用的能力各不相同。尽管缺乏与p55的结合，但在小鼠CTLL细胞系上进行检测时，所有类似物均表现出显著的生物学活性。精氨酸-38和苯丙氨酸-42类似物对p70的解离常数与中等亲和力结合一致；在与高亲和力IL-2受体复合物结合时，p55的存在对Kd值没有显著影响。这些结果证实了IL-2中Bα螺旋作为p55受体结合位点的重要性，并支持了IL-2-IL-2受体相互作用的修正模型。
