Fish E N, Banerjee K, Arakawa T, Stebbing N
Research Institute, Hospital for Sick Children, Toronto, Canada.
Drug Des Deliv. 1988 Feb;2(3):191-206.
Structure/function relationships for human gamma interferon (IFN-gamma) were investigated using recombinant DNA-derived homologues produced in E. coli. The various biological effects examined were antiviral, growth inhibitory and 2-5A synthetase activities, as well as receptor binding characteristics. Specific structural changes led to IFN-gamma homologues with defined alterations in biological activities. Amino acid residue changes at the hydrophobic core of the molecule resulted in two homologues exhibiting loss of affinity for the IFN-gamma receptor and dramatically reduced biological activities. These diminished activities probably relate to the inability of the homologues to form appropriately folded structures. Residue changes at two sites associated with beta-turns on the surface of IFN-gamma likewise resulted in homologues with reduced biological activities. In these cases, the reduced biological activities were not associated with reduced receptor binding. Addition of cysteine-tyrosine-cysteine to the amino-terminus of IFN-gamma, known to perturb the protein conformation, slightly reduced the affinity of the so-derived homologue for the IFN-gamma receptor on T98G cells, and there was concommitant reduction in biological activities. Experiments with a monoclonal antibody that binds to the carboxy-terminus of IFN-gamma indicated that this region of the molecule may not influence antiviral or antiproliferative activities. Overall our data imply that several sites along the IFN-gamma polypeptide contribute to biological activity, and that receptor binding and effector sites are distinct.
利用在大肠杆菌中产生的重组 DNA 衍生的同源物，对人γ干扰素（IFN-γ）的结构/功能关系进行了研究。所检测的各种生物学效应包括抗病毒、生长抑制和 2-5A 合成酶活性，以及受体结合特性。特定的结构变化导致 IFN-γ同源物的生物学活性发生特定改变。分子疏水核心处的氨基酸残基变化导致两种同源物对 IFN-γ受体的亲和力丧失，生物学活性显著降低。这些活性降低可能与同源物无法形成适当折叠的结构有关。IFN-γ表面与β-转角相关的两个位点的残基变化同样导致同源物的生物学活性降低。在这些情况下，生物学活性降低与受体结合减少无关。在 IFN-γ的氨基末端添加已知会扰乱蛋白质构象的半胱氨酸-酪氨酸-半胱氨酸，略微降低了由此产生的同源物对 T98G 细胞上 IFN-γ受体的亲和力，并且生物学活性随之降低。用结合 IFN-γ羧基末端的单克隆抗体进行的实验表明，分子的这一区域可能不影响抗病毒或抗增殖活性。总体而言，我们的数据表明，IFN-γ多肽上的几个位点对生物学活性有贡献，并且受体结合位点和效应位点是不同的。
