Demonstration by pulsed neutron scattering that the arrangement of the Fab and Fc fragments in the overall structures of bovine IgG1 and IgG2 in solution is similar.
Demonstration by pulsed neutron scattering that the arrangement of the Fab and Fc fragments in the overall structures of bovine IgG1 and IgG2 in solution is similar.
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通过脉冲中子散射证明溶液中牛IgG1和IgG2整体结构中Fab和Fc片段的排列相似。
DOI：
10.1042/bj3110283
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发表时间：
1995
期刊：
影响因子：
--
通讯作者：
Perkins
中科院分区：
文献类型：
--
作者：
M. Mayans;W. John;J Coadwell;D. Beale;Derek B. A. SYMONSt;J. Stephen;Perkins
牛 IgG1 和 IgG2 同种型在效应器功能上表现出很大差异。为了检查其结构基础，使用最近开发的相机 LOQ 通过脉冲中子散射研究了 IgG1 和 IgG2 的 12 结构域结构。该方法报告了 IgG 中 Fab 和 Fc 片段在溶液中的平均相对分布。发现 100% 2H2O 缓冲液中 IgG1 和 IgG2 的回转半径 (RG) 分别在 5.64 和 5.71 nm 处相似。两个横截面回转半径 (RXS) 也相似，分别为 2.38-2.41 和 0.98-1.02 nm。猪 IgG 也获得了类似的值。牛 IgG1 和 IgG2 都具有相似的整体溶液结构，尽管其结构中心的铰链区存在序列差异。开发了一种可能的 IgG 结构的自动计算机调查，其中两个 Fab 片段的坐标相对于 Fc 片段的坐标在二维平面中以 0.25 nm 的步长位移。发现从这些结构计算出的散射曲线对三个碎片的相对位移敏感，但对它们绕最长轴的旋转方向不敏感。使用平面 IgG 模型获得了与溶液散射数据良好的一致性，其中 IgG1 和 IgG2 中 Fab 的 CH1 结构域的 C 末端距 Fc 的 N 末端均为 3.6 nm，精度为 0.7 nm。能量精炼表明这种空间分离与牛 IgG1 和 IgG2 的铰链序列兼容。结果表明，可以使用 LOQ 数据对多域蛋白质结构进行建模，并且长铰链序列不一定反映 Fab 和 Fc 之间的较大距离。对于 IgG1 和 IgG2，Fc 位点与细胞表面 Fc 受体和补体 C1q 相互作用的空间可及性大体相似，并且 IgG1 和 IgG2 之间效应器功能的差异可能是基于 IgG2 铰链序列的缺失。
The bovine IgG1 and IgG2 isotypes exhibit large differences in effector functions. To examine the structural basis for this, the 12-domain structures of IgG1 and IgG2 were investigated by pulsed neutron scattering using a recently developed camera LOQ. This method reports on the average relative disposition in solution of the Fab and Fc fragments in IgG. The radii of gyration (RG) were found to be similar at 5.64 and 5.71 nm for IgG1 and IgG2 respectively in 100% 2H2O buffers. The two cross-sectional radii of gyration (RXS) were also similar at 2.38-2.41 and 0.98-1.02 nm. Similar values were obtained for porcine IgG. Both bovine IgG1 and IgG2 possess similar overall solution structures, despite sequence differences at the hinge region at the centre of their structures. An automated computer survey of possible IgG structures was developed, in which coordinates for the two Fab fragments were displaced in a two-dimensional plane relative to those of the Fc fragment in 0.25 nm steps. The scattering curves calculated from these structures were found to be sensitive to relative displacements of the three fragments, but not on their rotational orientation about their longest axes. Good agreement with the solution scattering data was obtained with a planar IgG model in which the C-terminus of the CH1 domain of Fab was 3.6 nm from the N-terminus of Fc in both IgG1 and IgG2, with a precision of 0.7 nm. Energy refinement showed that this spatial separation is compatible with the hinge sequences of bovine IgG1 and IgG2. The results show that multidomain protein structures can be modelled using LOQ data, and that a long hinge sequence does not necessarily reflect a large distance between Fab and Fc. The steric accessibility of Fc sites for interactions with cell-surface Fc receptors and C1q of complement is shown to be generally similar for IgG1 and IgG2, and the difference in effector function between IgG1 and IgG2 is probably based on deletions in the IgG2 hinge sequence.