Mechanism of E-cadherin dimerization probed by NMR relaxation dispersion
Mechanism of E-cadherin dimerization probed by NMR relaxation dispersion
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DOI：
10.1073/pnas.1314303110
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发表时间：
2013-10-08
影响因子：
11.1
通讯作者：
Palmer, Arthur G., III
中科院分区：
文献类型：
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作者：
Li, Ying;Altorelli, Nicole L.;Palmer, Arthur G., III
上皮钙粘蛋白（E-cadherin）是经典的钙粘蛋白家族成员，介导钙依赖性的嗜同性细胞间粘附。经典钙粘蛋白的晶体结构揭示了两个原聚体之间N-末端β-链相互交换的粘合剂二聚体界面。以前的工作已经确定了一个假定的中间体（称为“X-二聚体”）的野生型E-钙粘蛋白EC 1-EC2域的二聚化途径，基于晶体结构的突变体不能链交换和减速的结合动力学的突变在X-二聚体界面。在目前的工作中，NMR弛豫色散光谱被用来直接观察和表征中间状态，而不需要通过诱变破坏链交换结合界面。结果表明，E-钙粘蛋白形成链交换的二聚体主要是通过一种机制，在该机制中，形成一个弱的和短暂的X-二聚体样状态之前的成熟的链交换的二聚体结构的形成所需的构象变化。通过突变破坏这种中间状态会使结合和解离速率降低约10倍（4），同时最小限度地干扰亲和力。X-二聚体界面降低了与链交换相关的能垒，并使E-钙粘蛋白能够以与粘附连接中的停留时间一致的速率形成链交换的二聚体。
Epithelial cadherin (E-cadherin), a member of the classical cadherin family, mediates calcium-dependent homophilic cell-cell adhesion. Crystal structures of classical cadherins reveal an adhesive dimer interface featuring reciprocal exchange of N-terminal beta-strands between two protomers. Previous work has identified a putative intermediate (called the "X-dimer") in the dimerization pathway of wild-type E-cadherin EC1-EC2 domains, based on crystal structures of mutants not capable of strand swapping and on deceleration of binding kinetics by mutations at the X-dimer interface. In the present work, NMR relaxation dispersion spectroscopy is used to directly observe and characterize intermediate states without the need to disrupt the strand-swapped binding interface by mutagenesis. The results indicate that E-cadherin forms strand-swapped dimers predominantly by a mechanism in which formation of a weak and short-lived X-dimer-like state precedes the conformational changes required for formation of the mature strand-swapped dimeric structure. Disruption of this intermediate state through mutation reduces both association and dissociation rates by factors of similar to 10(4), while minimally perturbing affinity. The X-dimer interface lowers the energy barrier associated with strand swapping and enables E-cadherins to form strand-swapped dimers at a rate consistent with residence times in adherens junctions.