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首页> 外文期刊>Journal of Molecular Biology >Crystal structure of human RNA helicase A (DHX9): structural basis for unselective nucleotide base binding in a DEAD-box variant protein.
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Crystal structure of human RNA helicase A (DHX9): structural basis for unselective nucleotide base binding in a DEAD-box variant protein.

机译：人RNA解旋酶A（DHX9）的晶体结构：DEAD-box变异蛋白中非选择性核苷酸碱基结合的结构基础。

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摘要

RNA helicases of the DExD/H-box superfamily are critically involved in all RNA-related processes. No crystal structures of human DExH-box domains had been determined previously, and their structures were difficult to predict owing to the low level of homology among DExH-motif-containing proteins from diverse species. Here we present the crystal structures of the conserved domain 1 of the DEIH-motif-containing helicase DHX9 and of the DEAD-box helicase DDX20. Both contain a RecA-like core, but DHX9 differs from DEAD-box proteins in the arrangement of secondary structural elements and is more similar to viral helicases such as NS3. The N-terminus of the DHX9 core contains two long alpha-helices that reside on the surface of the core without contributing to nucleotide binding. The RNA-polymerase-II-interacting minimal transactivation domain sequence forms an extended loop structure that resides in a hydrophobic groove on the surface of the DEIH domain. DHX9 lacks base-selective contacts and forms an unspecific but important stacking interaction with the base of the bound nucleotide, and our biochemical analysis confirms that the protein can hydrolyze ATP, guanosine 5'-triphosphate, cytidine 5'-triphosphate, and uridine 5'-triphosphate. Together, these findings allow the localization of functional motifs within the three-dimensional structure of a human DEIH helicase and show how these enzymes can bind nucleotide with high affinity in the absence of a Q-motif.
机译：DExD / H-box超家族的RNA解旋酶至关重要地参与了所有与RNA相关的过程。以前尚未确定人DExH-box域的晶体结构，由于来自不同物种的含DExH-基序的蛋白质之间的同源性较低，因此难以预测其结构。在这里，我们介绍了包含DEIH-基序的解旋酶DHX9和DEAD-box解旋酶DDX20的保守域1的晶体结构。两者都包含一个RecA样的核心，但DHX9在二级结构元件的排列上与DEAD-box蛋白不同，并且更类似于病毒解旋酶（如NS3）。 DHX9核心的N端包含两个长的α-螺旋，它们位于核心的表面上而无助于核苷酸结合。与RNA聚合酶II相互作用的最小反式激活结构域序列形成了一个延伸的环结构，该结构位于DEIH结构域表面的疏水槽中。 DHX9缺乏碱基选择性接触，并与结合核苷酸的碱基形成非特异性但重要的堆积相互作用，我们的生化分析证实该蛋白质可以水解ATP，鸟苷5'-三磷酸，胞苷5'-三磷酸和尿苷5' -三磷酸。总之，这些发现允许功能性基序在人DEIH解旋酶的三维结构内定位，并表明这些酶如何在不存在Q-基序的情况下以高亲和力结合核苷酸。

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