Istituto Pasteur - Fondazione Cenci Bolognetti, Dipartimento di Scienze Biochimiche "A. Rossi Fanelli," Istituto di Biologia e Patologia Molecolari del CNR, Sapienza Università di Roma, Rome, Italy.
Architecture et Fonction des Macromolécules Biologiques, UMR 7257, National Centre for Scientific Research, Aix-Marseille Université, Marseille, France.
Biophys J. 2018 Apr 24;114(8):1889-1894. doi: 10.1016/j.bpj.2018.03.017.
The mechanism of interaction of an intrinsically disordered protein (IDP) with its physiological partner is characterized by a disorder-to-order transition in which a recognition and a binding step take place. Even if the mechanism is quite complex, IDPs tend to bind their partner in a cooperative manner such that it is generally possible to detect experimentally only the disordered unbound state and the structured complex. The interaction between the disordered C-terminal domain of the measles virus nucleoprotein (N) and the X domain (XD) of the viral phosphoprotein allows us to detect and quantify the two distinct steps of the overall reaction. Here, we analyze the robustness of the folding of N upon binding to XD by measuring the effect on both the folding and binding steps of N when the structure of XD is modified. Because it has been shown that wild-type XD is structurally heterogeneous, populating an on-pathway intermediate under native conditions, we investigated the binding to 11 different site-directed variants of N of one particular variant of XD (I504A XD) that populates only the native state. Data reveal that the recognition and the folding steps are both affected by the structure of XD, indicating a highly malleable pathway. The experimental results are briefly discussed in the light of previous experiments on other IDPs.
无规卷曲蛋白 (IDP) 与其生理伴侣相互作用的机制的特点是无序到有序的转变，其中包括识别和结合两个步骤。即使机制相当复杂，IDP 也倾向于以协同的方式与其伴侣结合，以至于通常只能实验检测到无规卷曲的未结合状态和结构复杂的复合物。麻疹病毒核蛋白 (N) 的无规卷曲 C 末端结构域与病毒磷蛋白的 X 结构域 (XD) 之间的相互作用使我们能够检测和量化整个反应的两个不同步骤。在这里，我们通过测量 XD 结构修饰对 N 的折叠和结合步骤的影响来分析 N 与 XD 结合时的折叠稳定性。由于已经表明野生型 XD 在结构上是异构的，在天然条件下会形成一种途径中间物，因此我们研究了 N 与 XD 的 11 种不同定点突变体的结合情况，其中包括一种特定 XD 变体 (I504A XD)，它只存在于天然状态。数据表明，识别和折叠步骤都受到 XD 结构的影响，表明这是一个高度可塑的途径。根据以前对其他 IDP 的实验结果，简要讨论了实验结果。
