Forced unfolding modulated by disulfide bonds in the Ig domains of a cell adhesion molecule
Forced unfolding modulated by disulfide bonds in the Ig domains of a cell adhesion molecule
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DOI：
10.1073/pnas.031409698
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发表时间：
2001-02-13
影响因子：
11.1
通讯作者：
Discher, DE
中科院分区：
文献类型：
--
作者：
Carl, P;Kwok, CH;Discher, DE
细胞粘附分子 (CAM) 通过细胞外域介导细胞附着和应力传递。在这里，我们强制展开包含域内二硫键的原型 Ig 超家族 CAM 的 Ig 结构域。所有此类 CAM 的 Ig 结构域均具有与钙粘蛋白胞外结构域、肌联蛋白 Ig 型结构域和纤连蛋白 III 型 (FNIII) 结构域同源的构象。原子力显微镜已被用来在二硫键保持完整或通过还原破坏的条件下延伸 Mel-CAM（黑色素瘤 CAM）的五个 Ig 结构域（一种在转移性黑色素瘤中过度表达的蛋白质）。在域内二硫键完整的生理条件下，在比之前报道的肌动蛋白的 Ig 型结构域或生腱蛋白的 FNIII 结构域小得多的力下观察到部分解折叠。这种在低力下的部分展开可能是赋予细胞-细胞接触弹性的重要机制，也是粘附相互作用的调节机制。在还原条件下，Mel-CAM 的 Ig 结构域在稍高的力下通过部分折叠状态完全展开。结果表明，在所有这些结构域的发散演化中，二硫键赋予的稳定性放宽了对强、非共价、折叠态相互作用的要求。
Cell adhesion molecules (CAMs) mediate cell attachment and stress transfer through extracellular domains. Here we forcibly unfold the Ig domains of a prototypical Ig superfamily CAM that contains intradomain disulfide bonds. The Ig domains of all such CAMs have conformations homologous to cadherin extracellular domains, titin Ig-type domains, and fibronectin type-ill (FNIII) domains. Atomic force microscopy has been used to extend the five Ig domains of Mel-CAM (melanoma CAM)-a protein that is overexpressed in metastatic melanomas-under conditions where the disulfide bonds were either left intact or disrupted through reduction. Under physiological conditions where intradomain disulfide bonds are intact, partial unfolding was observed at forces far smaller than those reported previously for either titin's Ig-type domains or tenascin's FNIII domains. This partial unfolding under low force may be an important mechanism for imparting elasticity to cell-cell contacts, as well as a regulatory mechanism for adhesive interactions. Under reducing conditions, Mel-CAM's Ig domains were found to fully unfold through a partially folded state and at slightly higher forces. The results suggest that, in divergent evolution of all such domains, stabilization imparted by disulfide bonds relaxes requirements for strong, noncovalent, folded-state interactions.