Leinikki P O, Calderon J, Luquette M H, Schreiber R D
Department of Pathology, Washington University School of Medicine, St. Louis, MO 63110.
J Immunol. 1987 Nov 15;139(10):3360-6.
Treatment of recombinant human interferon-gamma (IFN-gamma) with either 1) the arginine-specific proteases clostripain or submaxillaris protease or 2) the broadly specific enzyme pronase produced a stable fragment with m.w. of 15,500. Structural analysis showed that the cleavage occurred between residues 129 and 130 and thus produced a fragment lacking only 11 carboxyl-terminal amino acids. The fragmented and untreated molecules showed identical amino-terminal amino acid sequences and were equally reactive with either polyclonal or monoclonal anti-IFN-gamma. IFN-gamma lacking carboxyl-terminal amino acids displayed a 1000- to 2000-fold reduction in its capacity to bind to cellular IFN-gamma receptors at 4 degrees C. Functionally the fragment showed a 50-fold reduction in its ability to induce antiviral activity in fibroblasts and a 10-fold reduction in its ability to induce Fc receptors on the human histiocytic lymphoma cell line U937. These results thus suggest that the carboxyl terminus of human IFN-gamma contributes significantly to the formation of the receptor-binding site of the molecule.
用以下两种方法处理重组人干扰素-γ（IFN-γ）：1）用精氨酸特异性蛋白酶梭菌蛋白酶或颌下腺蛋白酶；2）用广谱特异性酶链霉蛋白酶，均可产生分子量为15,500的稳定片段。结构分析表明，切割发生在第129位和第130位残基之间，因此产生的片段仅缺少11个羧基末端氨基酸。片段化分子和未处理分子显示出相同的氨基末端氨基酸序列，并且与多克隆或单克隆抗IFN-γ具有相同的反应性。缺少羧基末端氨基酸的IFN-γ在4℃下与细胞IFN-γ受体结合的能力降低了1000至2000倍。在功能上，该片段在成纤维细胞中诱导抗病毒活性的能力降低了50倍，在人组织细胞淋巴瘤细胞系U937上诱导Fc受体的能力降低了10倍。因此，这些结果表明，人IFN-γ的羧基末端对该分子受体结合位点的形成有显著贡献。
