Lateral self-assembly of E-cadherin directed by cooperative calcium binding
Lateral self-assembly of E-cadherin directed by cooperative calcium binding
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DOI：
10.1016/s0014-5793(97)01333-1
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发表时间：
1997-11-17
期刊：
影响因子：
3.5
通讯作者：
Ikura, M
中科院分区：
文献类型：
--
作者：
Alattia, JR;Ames, JB;Ikura, M
我们报道了重组Ecad12的Ca 2+结合特性，一种跨越上皮钙粘蛋白前两个重复序列的构建体，并证明了Ca 2+结合和二聚体形成之间的联系。沉降平衡和动态光散射实验表明，在10 mM Ca 2+存在下，Ecad12发生弱二聚化（Kd（P）= 0.17 mM），虽然在不存在Ca 2+的情况下没有检测到明显的二聚体形成，但在Ecad 12的电子显微镜图像中也观察到Ca 2+诱导的二聚化。我们从通过色氨酸荧光和流动透析监测的Ca 2+滴定实验得出结论，二聚化不影响Ca 2+的平衡结合常数。然而，随着蛋白质浓度的增加，钙结合的Hill系数从1.5增加到2.4，表明二聚体的形成在很大程度上有助于钙结合的协同性。基于这些观察和以前的晶体学研究，我们认为钙更可能作为几何对齐器，确保钙粘蛋白分子的正确组装，而不是简单的粘合剂。(C)1997年欧洲生物化学学会联合会。
We report the Ca2+ binding characteristics of recombinant Ecad12, a construct spanning the first two repeats of epithelial cadherin, and demonstrate the links between Ca2+ binding and dimer formation, Sedimentation equilibrium and dynamic light scattering experiments show that weak dimerization of Ecad12 occurs in the presence of 10 mM Ca2+ (K-d(P) = 0.17 mM), while no appreciable dimer formation was detected in the absence of Ca2+, Ca2+-induced dimerization was also observed in electron microscopy images of Ecad12, We conclude from Ca2+ titration experiments monitored by tryptophan fluorescence and flow dialysis that dimerization does not affect the equilibrium binding constant for Ca2+ However, the value of the Hill coefficient for Ca2+ binding increases from 1.5 to 2.4 as the protein concentration increases, showing that dimer formation largely contributes to the cooperativity in Ca2+ binding, Based on these observations and previous crystallographic studies, we propose that calcium acts more likely as a geometrical aligner ensuring the proper assembly of cadherin molecules, rather than a simple adhesive. (C) 1997 Federation of European Biochemical Societies.