THE MOLECULAR ORGANIZATION OF HUMAN ALPHA 2-MACROGLOBULIN. AN IMMUNO ELECTRON MICROSCOPIC STUDY WITH MONOCLONAL ANTIBODIES
THE MOLECULAR ORGANIZATION OF HUMAN ALPHA 2-MACROGLOBULIN. AN IMMUNO ELECTRON MICROSCOPIC STUDY WITH MONOCLONAL ANTIBODIES
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人类α2-巨球蛋白的分子组织。
DOI：
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发表时间：
1988
影响因子：
6.7
通讯作者：
F. van Leuven
中科院分区：
文献类型：
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作者：
E. Delain;M. Barrav;J. Tapon‐Bretaudiére;F. Pochon;F. van Leuven
电子显微镜是一种非常方便的方法，可以将单抗的表位定位在大分子的表面，以研究其三维结构。我们将这种免疫电子显微镜方法应用于人ct2-巨球蛋白(Ct2M)。29株抗α2M单抗分别与四种不同形式的a2M结合：天然和胰凝乳酶转化的四聚体，以及与二价阳离子解离得到的相应二聚体。这些单抗可分为三类：1)H-样转化分子，2)天然分子，3)能与两种形式的α2M反应的单抗。1)在类H的α2M特异性单抗中，有几个与转化的a2M的细胞受体识别的20kD结构域发生反应。该结构域位于每个单体的羧基末端。一个免疫球蛋白结合在类H形式的两个相邻末端。其他这种类型的单抗在非末端位置与α2M尖端结合。分子间的连接建立了交替的α2M和Ig G分子的聚合物。2)在天然的a2M特异性单抗中，有一些能抑制蛋白酶诱导的天然α2M的转化。这些单抗的结合部位显示在天然半分子上。其中一株单抗还能与转化的二聚体发生反应，其区域很可能与四聚体转化的α2M分子中的一个不可及的表位相对应。3)在该类型的单抗中，只有两个单抗能够抑制α-2M的转化。显然，它们的表位应该接近α2M的诱饵区域。与两种α2M形式反应的其他单抗均不能抑制α2M的转化。所有这些单抗都可以通过与各种形式的α2M形成的免疫复合物的结构来区分。与天然分子相比，表位更容易定位在二聚体和类H转化的α2M上。根据这些观察，我们提出了一个新的模型来描述人α2M在其天然和转换的构型中的三维组织，以及它的蛋白酶诱导的转换。
Electron microscopy is a very convenient method to localize the epitopes of monoclonal antibodies (mAbs) at the surface of macromolecules for studying their tree-dimensional organization. We applied this immuno-electron microscopic method to human ct2-macroglobulin (ct2M). 29 anti-α2M mAbs have been tested with the four different forms of a2M : native and chymotrypsin-transformed tetramers, and the corresponding dimers, obtained by dissociation with divalent cations. These mAbs can be classified in three types : those which are specific for 1) the H-like transformed molecules, 2) the native molecules, and 3) those which can react with both forms of α2M. 1) Among the H-like α2M specific mAbs, several react with the 20 kD-domain which is recognized by the cellular receptor of transformed a2M. This domain is located at the carboxyterminal end of each monomer. One IgG binds to the end of two adjacent tips of the H-like form. The other mAbs of this type bind to the α2M tips at non-terminal positions. Intermolecular connections built polymers of alternating α2M and IgG molecules. 2) Among the native a2M-specific mAbs some are able to inhibit the protease-induced transformation of the native α2M. The binding sites of these mAbs are demonstrated on the native half-molecules. One of these mAbs was also able to react with transformed dimers, in a region corresponding very likely to an inaccessible epitope in the tetrameric transformed α2M molecule. 3) Among the mAbs of this type, only two were able to inhibit the protease-induced transformation of α2M. Obviously, their epitopes should be close to the bait region of α2M. The other mAbs reacting with both α2M forms did not inhibit the α2M transformation. All these mAbs can be distinguished by the structure of the immune complexes formed with all forms of α2M. The epitopes are more easily located on the dimers and on the H-like transformed α2M than on the native molecules. From these observations, we propose a new model of the tree-dimensional organization of the human α2M in its native and transformed configurations, and of its protease-induced transformation.