Savino R, Lahm A, Giorgio M, Cabibbo A, Tramontano A, Ciliberto G
Instituto di Ricerche di Biologia Molecolare, P. Angeletti, Pomezia, Rome, Italy.
Proc Natl Acad Sci U S A. 1993 May 1;90(9):4067-71. doi: 10.1073/pnas.90.9.4067.
Interleukin 6 is a 184-aa polypeptide postulated to belong to the class of helical cytokines. We built a three-dimensional model of human interleukin 6 based on the similarity of its hydrophobicity pattern with that of other cytokines and on the x-ray structure of growth hormone, interleukin 2, interleukin 4, interferon beta, and granulocyte-macrophage colony-stimulating factor. The resulting model is a bundle of four alpha-helices and suggests possible alternative conformations for the 9 C-terminal amino acids; in this region, the importance of Arg-182 and Met-184 for biological activity has been demonstrated [Lutticken, C., Kruttgen, A., Moller, C., Heinrich, P.C. & Rose-John, S. (1991) FEBS Lett. 282, 265-267]. Therefore, we generated a large collection of single-amino acid variants in residues 175-181. Analysis of their biological activity in two systems and the receptor binding properties of a subset of the mutants indicates that the entire region is involved in forming the receptor binding surface and supports the hypothesis that this region does not assume an alpha-helical conformation. Remarkably, we also found a mutant with receptor affinity and biological activity much higher than wild type; the potential therapeutical value of this finding is discussed.
白细胞介素6是一种由184个氨基酸组成的多肽，被认为属于螺旋细胞因子类。我们基于其疏水模式与其他细胞因子的相似性以及生长激素、白细胞介素2、白细胞介素4、干扰素β和粒细胞-巨噬细胞集落刺激因子的X射线结构，构建了人白细胞介素6的三维模型。所得模型是由四条α螺旋组成的束状结构，并提示了9个C末端氨基酸可能的替代构象；在该区域，已证明精氨酸-182和甲硫氨酸-184对生物活性的重要性[卢蒂肯斯，C.，克鲁特根，A.，莫勒，C.，海因里希，P.C.和罗斯-约翰，S.（1991年）《欧洲生物化学学会联合会快报》282，265 - 267]。因此，我们在175 - 181位残基中生成了大量单氨基酸变体。对它们在两个系统中的生物活性以及一部分突变体的受体结合特性的分析表明，整个区域都参与形成受体结合表面，并支持该区域不呈现α螺旋构象的假说。值得注意的是，我们还发现了一个受体亲和力和生物活性比野生型高得多的突变体；讨论了这一发现的潜在治疗价值。
