Department of Biology, University of Copenhagen, Ole Maaloes Vej 5, DK-2200 Kobenhavn N, Denmark.
Proc Natl Acad Sci U S A. 2010 Jul 13;107(28):12535-40. doi: 10.1073/pnas.1001693107. Epub 2010 Jun 24.
Native molten globules are the most folded kind of intrinsically disordered proteins. Little is known about the mechanism by which native molten globules bind to their cognate ligands to form fully folded complexes. The nuclear coactivator binding domain (NCBD) of CREB binding protein is particularly interesting in this respect as structural studies of its complexes have shown that NCBD folds into two remarkably different states depending on the ligand being ACTR or IRF-3. The ligand-free state of NCBD was characterized in order to understand the mechanism of folding upon ligand binding. Biophysical studies show that despite the molten globule nature of the domain, it contains a small cooperatively folded core. By NMR spectroscopy, we have demonstrated that the folded core of NCBD has a well ordered conformer with specific side chain packing. This conformer resembles the structure of the NCBD in complex with the protein ligand, ACTR, suggesting that ACTR binds to prefolded NCBD molecules from the ensemble of interconverting structures.
天然无规卷曲的蛋白质是最具折叠状态的无序蛋白质。对于天然无规卷曲的蛋白质如何与相应的配体结合形成完全折叠的复合物，人们知之甚少。在这方面，CREB 结合蛋白的核共激活剂结合结构域（NCBD）特别有趣，因为对其复合物的结构研究表明，NCBD 根据配体 ACTR 或 IRF-3 的不同而折叠成两种截然不同的状态。为了了解配体结合时的折叠机制，对 NCBD 的无配体状态进行了表征。生物物理研究表明，尽管该结构域具有无规卷曲的性质，但它包含一个小的协同折叠核心。通过 NMR 光谱，我们已经证明 NCBD 的折叠核心具有有序的构象，具有特定的侧链堆积。这种构象类似于与蛋白质配体 ACTR 结合的 NCBD 的结构，表明 ACTR 从相互转化的结构的集合中结合到预折叠的 NCBD 分子上。
