The spliceosome consists of five small RNAs and more than 100 proteins. Almost 50% of the human spliceosomal proteins were predicted to be intrinsically disordered or to contain disordered regions, among them the G-patch protein Spp2. The G-patch region of Spp2 binds to the DEAH-box ATPase Prp2, and both proteins together are essential for promoting the transition from the Bact to the catalytically active B* spliceosome. Here we show by circular dichroism and nuclear magnetic resonance (NMR) spectroscopy that Spp2 is intrinsically disordered in solution. Crystal structures of a complex consisting of Prp2-ADP and the G-patch domain of Spp2 demonstrate that the G-patch gains a defined fold when bound to Prp2. While the N-terminal region of the G-patch always folds into an α-helix in five different crystal structures, the C-terminal part is able to adopt two alternative conformations. NMR studies further revealed that the N-terminal part of the Spp2 G-patch, which is the most conserved region in different G-patch proteins, transiently samples helical conformations, possibly facilitating a conformational selection binding mechanism. The structural analysis unveils the role of conserved residues of the G-patch in the dynamic interaction mode of Spp2 with Prp2, which is vital to maintain the binding during the Prp2 domain movements needed for RNA translocation.

中文翻译：

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本质上无序的剪接因子Spp2及其与DEAH-box ATPase Prp2的结合的结构分析。

剪接体由5个小RNA和100​​多个蛋白质组成。预测将近50％的人类剪接体蛋白是内在无序的或包含无序的区域，其中包括G斑蛋白Spp2。Spp2的G-patch区与DEAH-box ATPase Prp2结合，并且这两种蛋白一起对于促进从细菌向具有催化活性的B *剪接体的转变至关重要。在这里，我们通过圆二色性和核磁共振（NMR）光谱表明，Spp2在溶液中固有地无序。由Prp2-ADP和Spp2的G-patch域组成的复合物的晶体结构表明，与Prp2结合时，G-patch具有确定的倍数。虽然G色块的N端区域总是以五种不同的晶体结构折叠成α螺旋，C端部分可以采用两种替代的构型。NMR研究进一步表明，Spp2 G补丁的N端部分是不同G补丁蛋白中最保守的区域，它会瞬时采样螺旋构象，可能有助于构象选择结合机制。结构分析揭示了G斑的保守残基在Spp2与Prp2的动态相互作用模式中的作用，这对于维持RNA移位所需的Prp2域移动期间的结合至关重要。