A new crystal structure, Ca2+ dependence and mutational analysis reveal molecular details of E-cadherin homoassociation
A new crystal structure, Ca2+ dependence and mutational analysis reveal molecular details of E-cadherin homoassociation
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DOI：
10.1093/emboj/18.7.1738
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发表时间：
1999-04-01
期刊：
影响因子：
11.4
通讯作者：
Engel, J
中科院分区：
文献类型：
--
作者：
Pertz, O;Bozic, D;Engel, J
ECADCOMP 是一种重组 E-钙粘蛋白胞外域，由软骨寡聚基质蛋白的组装结构域五聚化，ECADCOMP 的电子显微镜已用于分析顺式二聚化和反式相互作用在该细胞粘附分子的同源缔合中的作用。研究了两种相互作用的 Ca2+ 依赖性。低 Ca2+ 浓度 (50 μM) 稳定了 E-钙粘蛋白的棒状结构。在中等 Ca2+ 浓度（500 μM）下，五聚体中两个相邻的胞外域形成顺式二聚体。在高 Ca2+ 浓度 (>1 mM) 下，来自不同五聚体的两个顺式二聚体形成反式相互作用。 E-钙粘蛋白 N 端结构域对的 X 射线结构显示，每个不对称单元有两个分子，呈相互扭曲的 X 形排列，结构域 1 和结构域 2 之间的 Ca2+ 结合区域接触最紧密。与之前的数据相反，Trp2 对接在其自身分子的疏水空腔中，因此不参与两个分子的顺式二聚化。 ECADCOMP 中的 W2A 和 A80I（参与 Trp2 周围疏水腔的残基）突变进一步支持了这一点，这两种突变都导致反式相互作用的消除，但不导致顺式相互作用的消除。结构和生化数据表明毫摩尔范围内的 Ca2+ 结合与 Trp2 对接之间存在联系，这两个事件对于反式关联都是必需的。
Electron microscopy of ECADCOMP, a recombinant E-cadherin ectodomain pentamerized by the assembly domain of cartilage oligomeric matrix protein, has been used to analyze the role of cis-dimerization and trans-interaction in the homophilic association of this cell adhesion molecule. The Ca2+ dependency of both interactions was investigated. Low Ca2+ concentrations (50 mu M) stabilized the rod-like structure of E-cadherin. At medium Ca2+ concentration (500 mu M), two adjacent ectodomains in a pentamer formed cis-dimers. At high Ca2+ concentration (>1 mM), two cis-dimers from different pentamers formed a trans-interaction. The X-ray structure of an N-terminal domain pair of E-cadherin revealed two molecules per asymmetric unit in an intertwisted X-shaped arrangement with closest contacts in the Ca2+-binding region between domains 1 and 2, Contrary to previous data, Trp2 was docked in the hydrophobic cavity of its own molecule, and was therefore not involved in cis-dimerization of two molecules. This was supported further by W2A and A80I (a residue involved in the hydrophobic cavity surrounding Trp2) mutations in ECADCOMP which both led to abrogation of the trans- but not the cis-interaction. Structural and biochemical data suggest a link between Ca2+ binding in the millimolar range and Trp2 docking, both events being essential for the trans-association.