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首页> 外文期刊>Journal of Molecular Biology >Crystal structure of conserved domains 1 and 2 of the human DEAD-box helicase DDX3X in complex with the mononucleotide AMP
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Crystal structure of conserved domains 1 and 2 of the human DEAD-box helicase DDX3X in complex with the mononucleotide AMP

机译：与单核苷酸AMP复合的人DEAD-box解旋酶DDX3X保守结构域1和2的晶体结构

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摘要

DExD-box helicases are involved in all aspects of cellular RNA metabolism. Conserved domains 1 and 2 contain nine signature motifs that are responsible for nucleotide binding, RNA binding and ATP hydrolysis. The human DEAD-box helicase DDX3X has been associated with several different cellular processes, such as; cell-growth control, mRNA transport and translation, and is suggested to be essential for the export of unspliced/ partially spliced HIV mRNAs from the nucleus to the cytoplasm. Here, the crystal structure of conserved domains 1 and 2 of DDX3X, including a DDX3-specific insertion that is not generally found in human DExD-box helicases, is presented. The N-terminal domain 1 and the C-terminal domain 2 both display RecA-like folds comprising a central beta-sheet flanked by alpha-helices. Interestingly, the DDX3X-specific insertion forms a helical element that extends a highly positively charged sequence in a loop, thus increasing the RNA-binding surface of the protein. Surprisingly, although DDX3X was crystallized in the presence of a large excess of ADP or the slowly hydrolyzable ATP analogue ATP gamma S the contaminant AMP was seen in the structure. A fluorescent-based stability assay showed that the thermal stability of DDX3X was increased by the mononucleotide AMP but not by ADP or ATP gamma S, suggesting that DDX3X is stabilized by AMP and elucidating why AMP was found in the nucleotide-binding pocket. (c) 2007 Elsevier Ltd. All rights reserved.
机译：DExD-box解旋酶参与细胞RNA代谢的所有方面。保守的结构域1和2包含九个签名基序，负责核苷酸结合，RNA结合和ATP水解。人DEAD-box解旋酶DDX3X与几种不同的细胞过程相关，例如：细胞生长的控制，mRNA的运输和翻译，并建议对于未剪接/部分剪接的HIV mRNA从细胞核输出到细胞质至关重要。在这里，介绍了DDX3X保守域1和2的晶体结构，包括在人DExD-box解旋酶中通常没有的DDX3特异性插入。 N末端结构域1和C末端结构域2都显示RecA样的折叠，其中包括一个中央β-折叠，两侧是α-螺旋。有趣的是，DDX3X特异性插入形成一个螺旋元件，该元件在环中延伸了一个高度带正电的序列，从而增加了蛋白质的RNA结合表面。令人惊讶地，尽管DDX3X在大量过量的ADP或缓慢水解的ATP类似物ATPγS的存在下结晶，但在结构中发现了污染物AMP。基于荧光的稳定性分析表明，单核苷酸AMP可提高DDX3X的热稳定性，而ADP或ATPγS不会提高DDX3X的热稳定性，这表明DDX3X被AMP稳定，并阐明了为什么在核苷酸结合袋中发现了AMP。 （c）2007 Elsevier Ltd.保留所有权利。

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