Kellner Julian N, Meinhart Anton
Department of Biomolecular Mechanisms, Max Planck Institute for Medical Research, Jahnstrasse 29, 69120 Heidelberg, Germany.
Acta Crystallogr F Struct Biol Commun. 2015 Sep;71(Pt 9):1176-88. doi: 10.1107/S2053230X15013709. Epub 2015 Aug 25.
The human RNA helicase DDX1 in the DEAD-box family plays an important role in RNA processing and has been associated with HIV-1 replication and tumour progression. Whereas previously described DEAD-box proteins have a structurally conserved core, DDX1 shows a unique structural feature: a large SPRY-domain insertion in its RecA-like consensus fold. SPRY domains are known to function as protein-protein interaction platforms. Here, the crystal structure of the SPRY domain of human DDX1 (hDSPRY) is reported at 2.0 Å resolution. The structure reveals two layers of concave, antiparallel β-sheets that stack onto each other and a third β-sheet beneath the β-sandwich. A comparison with SPRY-domain structures from other eukaryotic proteins showed that the general β-sandwich fold is conserved; however, differences were detected in the loop regions, which were identified in other SPRY domains to be essential for interaction with cognate partners. In contrast, in hDSPRY these loop regions are not strictly conserved across species. Interestingly, though, a conserved patch of positive surface charge is found that may replace the connecting loops as a protein-protein interaction surface. The data presented here comprise the first structural information on DDX1 and provide insights into the unique domain architecture of this DEAD-box protein. By providing the structure of a putative interaction domain of DDX1, this work will serve as a basis for further studies of the interaction network within the hetero-oligomeric complexes of DDX1 and of its recruitment to the HIV-1 Rev protein as a viral replication factor.
DEAD盒家族中的人类RNA解旋酶DDX1在RNA加工过程中发挥着重要作用，并且与HIV-1复制及肿瘤进展相关。此前描述的DEAD盒蛋白具有结构保守的核心区域，而DDX1却展现出独特的结构特征：在其类RecA一致性折叠结构中有一个大的SPRY结构域插入。已知SPRY结构域可作为蛋白质-蛋白质相互作用平台。在此，报道了人类DDX1的SPRY结构域（hDSPRY）在2.0 Å分辨率下的晶体结构。该结构揭示出两层相互堆叠的凹形反平行β折叠片层，以及β三明治结构下方的第三层β折叠片层。与其他真核生物蛋白质的SPRY结构域结构进行比较发现，一般的β三明治折叠结构是保守的；然而，在环区检测到了差异，在其他SPRY结构域中这些环区被确定为与同源伴侣相互作用所必需。相比之下，在hDSPRY中，这些环区在不同物种间并不严格保守。不过，有趣的是，发现了一个保守的正表面电荷区域，它可能会取代连接环作为蛋白质-蛋白质相互作用表面。本文所呈现的数据包含了关于DDX1的首个结构信息，并为深入了解这种DEAD盒蛋白独特的结构域架构提供了见解。通过提供DDX1一个假定的相互作用结构域的结构，这项工作将为进一步研究DDX1异源寡聚复合物内的相互作用网络以及其作为病毒复制因子被招募至HIV-1 Rev蛋白的过程奠定基础。
