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首页> 外文期刊>Biochemistry >THE FC SEGMENT OF IGE INFLUENCES THE KINETICS OF DISSOCIATION OF A SYMMETRICAL BIVALENT LIGAND FROM CYCLIC DIMERIC COMPLEXES
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THE FC SEGMENT OF IGE INFLUENCES THE KINETICS OF DISSOCIATION OF A SYMMETRICAL BIVALENT LIGAND FROM CYCLIC DIMERIC COMPLEXES

机译：IGE的FC段影响对称双价配体从循环二元复合物中解离的动力学

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As part of a systematic effort to determine the features of immunoglobulin E-receptor (IgE-Fc epsilon RI) aggregation that are critical for cellular activation, we used fluorescence to examine the dissociation of a soluble bivalent ligand, N,N'-bis[[epsilon-[(2,4-dinitrophenyl)amino]caproyl]-L-tyrosyl]-L-cystine ((DCT)(2)-cys), from soluble bivalent IgE and its bivalent F(ab')(2) and monovalent Fab' fragments. Cross-linking of Fab' fragments by (DCT)(2)-cys is limited to linear dimers, and we find that (DCT)(2)-cys dissociation from Fab' occurs with a single kinetic coefficient [(4.2 +/- 0.6) x 10(-3) s(-1)] that corresponds to the lower of the two kinetic coefficients observed with the bivalent IgE [(4.7 +/- 0.7) x 10(-2) s(-1) and (4.4 +/- 0.3) x 10(-3) s(-1)]. Similarly, the lower value is obtained for dissociation of (DCT)(2)-cys that is monovalently bound to IgE after incubation with a large excess of the ligand. (DCT)(2)-cys can bind to bivalent F(ab')(2) fragments and form a variety of linear and cyclic aggregates, similarly to IgE, but, unlike IgE, we find that dissociation occurs with a single kinetic coefficient similar to that observed for Fab'. We find that IgE and its (Fab')(2) fragments form highly stable cyclic dimer rings with two (DCT)(2)-cys. We demonstrate that the kinetic coefficients are independent of enhanced fluorescence quenching observed for bound sites in cyclic dimers. Together, the results show that the rate constant for breaking a linear cross-link formed by (DCT)(2)-cys is the same as that for dissociation of the monovalently bound (DCT)(2)-cys. Further, they show that opening of a bond in a dimer ring for the F(ab')(2) fragment occurs with approximately the same dissociation rate constant as opening a bond in a linear cross-link. This rate constant is about three times smaller than that observed with IgE, suggesting that steric strain is caused by apposed Fc segments in cyclic IgE dimers. Such structural interference may affect the functional consequences of IgE-Fc epsilon RI aggregation on the cell surface.
机译：作为确定免疫球蛋白E受体（IgE-Fc epsilon RI）聚集特征对系统激活至关重要的系统工作的一部分，我们使用荧光检查了可溶性二价配体N，N'-bis [ [ε-[（2,4-二硝基苯基）氨基]己酰基] -L-酪氨酰] -L-胱氨酸（（DCT）（2）-cys），来自可溶性二价IgE及其二价F（ab'）（2）和单价Fab'片段。 （DCT）（2）-cys对Fab'片段的交联仅限于线性二聚体，我们发现（DCT）（2）-cys与Fab'的解离具有单个动力学系数[（4.2 +/- 0.6）x 10（-3）s（-1）]，对应于用二价IgE [（4.7 +/- 0.7）x 10（-2）s（-1）和（ 4.4 +/- 0.3）x 10（-3）s（-1）]。同样，在与大量过量的配体孵育后，单价结合到IgE的（DCT）（2）-cys的解离得到较低的值。 （DCT）（2）-cys可以与二价F（ab'）（2）片段结合并形成各种线性和环状聚集体，类似于IgE，但与IgE不同，我们发现解离发生时具有单个动力学系数与观察到的Fab'相似。我们发现IgE及其（Fab'）（2）片段与两个（DCT）（2）-cys形成高度稳定的环状二聚环。我们证明，动力学系数与环状二聚体中结合位点观察到的增强荧光猝灭无关。总之，结果表明，破坏由（DCT）（2）-cys形成的线性交联的速率常数与解离单价结合的（DCT）（2）-cys的速率常数相同。此外，他们表明，在F（ab'）（2）片段的二聚环中打开一个键，其解离速率常数与在线性交联中打开一个键几乎相同。该速率常数大约是用IgE观察到的速率常数的三倍，这表明空间应变是由环状IgE二聚体中的Fc段引起的。这样的结构干扰可能影响细胞表面上IgE-FcεRI聚集的功能后果。

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