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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- 作者：Patrick Schü ; tz ; Elisabet Wahlberg ; Tobias Karlberg ; Martin Hammarströ ; m ; Ruairi Collins ; Alex Flores ; Herwig Schü ; ler
- 关键词：RNA helicase ; RecA ; DExD/H-box ; nucleotide binding ; X-ray crystallography
- 刊名：Journal of Molecular Biology
- 出版年：2010
- 出版时间：23 July 2010
- 年：2010
- 卷：400
- 期：4
- 页码：768-782
- 全文大小：3348 K
文摘
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 α-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.