Masking of the Fc region in human IgG4 by constrained X-ray scattering modelling: implications for antibody function and therapy
Masking of the Fc region in human IgG4 by constrained X-ray scattering modelling: implications for antibody function and therapy
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DOI：
10.1042/bj20100641
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发表时间：
2010-11-15
影响因子：
4.1
通讯作者：
Dalby, Paul A.
中科院分区：
文献类型：
--
作者：
Abe, Yuki;Gor, Jayesh;Dalby, Paul A.
在人类免疫球蛋白抗体的四个亚类中，IgG4不能激活补体，并表现出非典型的自结合，包括形成双特异性抗体，这是值得关注的。抗体的溶液结构对于了解抗体的功能和治疗应用至关重要。因此，对IgG4进行了同步加速器X射线散射研究。随着浓度的增加，Guinier X射线的回转半径R-G从5.0 nm增加到5.1 nm。距离分布函数P(R)在0.3 mg/m l时出现单峰，在1.3 mg/m l时分解为两个峰，r值在1.3 mg/m l时变小，而最大尺寸在17 nm处不变。这表明IgG4溶液结构具有很小的浓度依赖性。通过分析超速离心法，测得S的沉淀值为6.4时，无浓度依赖性。约束散射模型的结果表明，IgG4具有不对称的溶液结构，其中一个Fab-Fc对比另一对更接近，Fe区域一侧的可及性被Fab区域掩盖。两个Fab-Fc对之间的平均距离随着IgG4浓度的变化而变化1-2 nm。Fab区的平均构象似乎能够阻止补体C1q与Fc区结合，并通过Fe区阻碍IgG4的自结合。目前的结果阐明了IgG4的功能，并为研究抗体的稳定性提供了一个起点。
Of the four human IgG antibody subclasses IgG1-IgG4, IgG4 is of interest in that it does not activate complement and exhibits atypical self-association, including the formation of bispecifie antibodies. The solution structures of antibodies are critical to understand function and therapeutic applications. Thus IgG4 was studied by synchrotron X-ray scattering. The Guinier X-ray radius of gyration R-G increased from 5.0 nm to 5.1 nm with an increase of concentration. The distance distribution function P(r) revealed a single peak at 0.3 mg/ml, which resolved into two peaks that shifted to smaller r values at 1.3 mg/ml, even though the maximum dimension of IgG4 was unchanged at 17 nm. This indicated a small concentration dependence of the IgG4 solution structure. By analytical ultracentrifugation, no concentration dependence in the sedimentation coefficient of 6.4 S was observed. Constrained scattering modelling resulted in solution structural determinations that showed that IgG4 has an asymmetric solution structure in which one Fab-Fc pair is closer together than the other pair, and the accessibility of one side of the Fe region is masked by the Fab regions. The averaged distances between the two Fab-Fc pairs change by 1-2 nm with the change in IgG4 concentration. The averaged conformation of the Fab regions appear able to hinder complement C1q binding to the Fc region and the self-association of IgG4 through the Fe region. The present results clarify IgG4 function and provide a starting point to investigate antibody stability.