Rousseaux-Prévost R, Rousseaux J, Bazin H, Biserte G
Int Arch Allergy Appl Immunol. 1983 Mar;70(3):268-76. doi: 10.1159/000233334.
The structural changes induced by heating rat IgE at 56 degrees C and relationship with loss of cytotropic activity were examinated in the present study. Circular dichroism spectrum of IgE heated at 56 degrees C showed irreversible changes in the peptide bond spectral regions: increase in beta-sheet structure, but no significant modifications in the aromatic side chain region. Thus, circular dichroism studies did not suggest important perturbations of the tertiary structure of the IgE molecule. Parallel studies with F(ab')2-epsilon fragment did not show significant alterations of either peptide bond or aromatic side chain spectral regions. Analysis of IgE heated at 56 degrees C by polyacrylamide gradient gel electrophoresis showed the presence of large amounts of polymeric material. Polymerization of IgE was found to increase with time of heating at 56 degrees C and to depend on protein concentration; polymerization was decreased at temperatures lower than 56 degrees C. A relationship between loss of cytotropic activity and the proportion of polymeric material in the heated IgE solutions was observed. Isolated polymeric molecules produced by heating showed considerable decrease in cytotropic activity whereas monomer isolated from heated IgE was found biologically active. The ability to form polymers is an intrinsic property of the carboxy-terminal domains C epsilon 3 and C epsilon 4, as the F(ab')2-epsilon fragment did not polymerize upon heating at 56 degrees C. A model of thermal inactivation of rat IgE is proposed in which aggregation of the carboxy-terminal domains of the epsilon-chain does not allow interaction of these domains with the monovalent IgE receptor of mast cells.
本研究检测了56℃加热大鼠IgE引起的结构变化及其与细胞otropic活性丧失的关系。56℃加热的IgE的圆二色光谱显示肽键光谱区域发生不可逆变化：β-折叠结构增加，但芳香侧链区域无明显修饰。因此，圆二色性研究未提示IgE分子三级结构有重要扰动。对F(ab')2-ε片段的平行研究未显示肽键或芳香侧链光谱区域有明显改变。通过聚丙烯酰胺梯度凝胶电泳分析56℃加热的IgE，发现存在大量聚合物质。发现IgE的聚合随56℃加热时间增加而增加，并取决于蛋白质浓度；在低于56℃的温度下聚合减少。观察到加热的IgE溶液中细胞otropic活性丧失与聚合物质比例之间的关系。加热产生的分离聚合分子细胞otropic活性显著降低，而从加热的IgE中分离的单体具有生物活性。形成聚合物的能力是羧基末端结构域Cε3和Cε4的固有特性，因为F(ab')2-ε片段在56℃加热时不会聚合。提出了大鼠IgE热失活模型，其中ε链羧基末端结构域的聚集不允许这些结构域与肥大细胞的单价IgE受体相互作用。
