Journal
JOURNAL OF MOLECULAR BIOLOGY
Volume 400, Issue 4, Pages 768-782Publisher
ACADEMIC PRESS LTD- ELSEVIER SCIENCE LTD
DOI: 10.1016/j.jmb.2010.05.046
Keywords
RNA helicase; RecA; DExD/H-box; nucleotide binding; X-ray crystallography
Categories
Funding
- Canadian Institutes for Health Research [1097737]
- Canada Foundation for Innovation
- Genome Canada
- Ontario Genomics Institute
- GlaxoSmithKline
- Karolinska Institutet
- Knut and Alice Wallenberg Foundation
- Ontario Innovation Trust
- Ontario Ministry for Research and Innovation
- Merck and Co., Inc.
- Novartis Research Foundation
- Swedish Agency for Innovation Systems
- Swedish Foundation for Strategic Research
- Wellcome Trust
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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 a-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. (C) 2010 Elsevier Ltd. All rights reserved.
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