Istituto Pasteur - Fondazione Cenci Bolognetti, Dipartimento di Scienze Biochimiche "A. Rossi Fanelli" and Istituto di Biologia e Patologia Molecolari del CNR, Sapienza Università di Roma, Rome, Italy.
Centre for Misfolding Diseases, Yusuf Hamied Department of Chemistry, University of Cambridge, Cambridge, UK.
Protein Sci. 2022 Sep;31(9):e4396. doi: 10.1002/pro.4396.
PDZ domains are the most diffused protein-protein interaction modules of the human proteome and are often present in tandem repeats. An example is PDZD2, a protein characterized by the presence of six PDZ domains that undergoes a proteolytic cleavage producing sPDZD2, comprising a tandem of two PDZ domains, namely PDZ5 and PDZ6. Albeit the physiopathological importance of sPDZD2 is well-established, the interaction with endogenous ligands has been poorly characterized. To understand the determinants of the stability and function of sPDZD2, we investigated its folding pathway. Our data highlights the presence of a complex scenario involving a transiently populated folding intermediate that may be accumulated from the concurrent denaturation of both PDZ5 and PDZ6 domains. Importantly, double jump kinetic experiments allowed us to pinpoint the ability of this transient intermediate to bind the physiological ligand of sPDZD2 with increased affinity compared to the native state. In summary, our results provide an interesting example of a functionally competent misfolded intermediate, which may exert a cryptic function that is not captured from the analysis of the native state only.
PDZ 结构域是人类蛋白质组中分布最广泛的蛋白质-蛋白质相互作用模块，并且经常以串联重复的形式存在。PDZD2 就是一个很好的例子，它是一种含有六个 PDZ 结构域的蛋白质，经过蛋白水解切割后产生 sPDZD2，由两个 PDZ 结构域（即 PDZ5 和 PDZ6）串联组成。尽管 sPDZD2 的生理病理重要性已得到充分证实，但对其与内源性配体的相互作用的研究还很不完善。为了了解 sPDZD2 的稳定性和功能的决定因素，我们研究了它的折叠途径。我们的数据突出了存在一种复杂的情况，涉及到一个短暂存在的折叠中间体，它可能是由 PDZ5 和 PDZ6 结构域的同时变性积累而来。重要的是，双跳跃动力学实验使我们能够确定这种瞬态中间体与 sPDZD2 的生理配体结合的能力，与天然状态相比，结合亲和力增加。总之，我们的结果提供了一个有趣的例子，说明了功能上有能力的错误折叠中间体，它可能发挥一种隐藏的功能，仅从天然状态的分析中无法捕捉到。
