Structural Biology, St. Jude Children's Research Hospital, 262 Danny Thomas Place, MS 311, Memphis, TN 38105, USA.
J Mol Biol. 2014 Jan 9;426(1):62-70. doi: 10.1016/j.jmb.2013.09.036. Epub 2013 Oct 10.
Intrinsically disordered regions in proteins play active roles in recognition, signaling and molecular sorting. They often undergo coupled folding and binding giving rise to largely ordered interfaces with their binding partners. The cytoplasmic region of the T-cell receptor zeta subunit (ζcyt) has been previously proposed to specifically dimerize in the absence of a disorder-to-order transition, suggesting an intriguing dimerization mechanism that may involve multiple transient interfaces. We show here using analytical ultracentrifugation, NMR, size-exclusion chromatography (SEC) and multi-angle light scattering that neither ζcyt nor the cytoplasmic region of CD3ε significantly populates a dimeric state but that they are mostly monomers in solution up to millimolar concentrations. They experience a salt- and concentration-dependent shift of their elution volume in SEC previously interpreted as dimerization. Our data show that ζcyt does not form a highly disordered protein complex and leaves open the question as to whether completely disordered dimers (or other oligomers) exist in nature.
蛋白质中的无规则区域在识别、信号传递和分子分类中发挥着积极的作用。它们经常经历折叠和结合的偶联，从而与它们的结合伙伴形成主要有序的界面。T 细胞受体 zeta 亚基（ζcyt）的细胞质区域先前被提出在没有无序到有序转变的情况下特异性二聚化，这表明存在一种有趣的二聚化机制，可能涉及多个瞬时界面。我们在这里使用分析超速离心、NMR、大小排阻色谱（SEC）和多角度光散射表明，ζcyt 或 CD3ε 的细胞质区域都不会显著形成二聚体状态，但在溶液中它们主要是单体，直到毫摩尔浓度。它们在 SEC 中的洗脱体积会发生盐和浓度依赖性的变化，以前曾将其解释为二聚化。我们的数据表明，ζcyt 不会形成高度无序的蛋白质复合物，这使得完全无序的二聚体（或其他低聚物）是否存在于自然界中的问题仍然存在。
