2I4I: Crystal Structure Of Human Dead-Box Rna Helicase Ddx3x

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 ATPgammaS 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 ATPgammaS, suggesting that DDX3X is stabilized by AMP and elucidating why AMP was found in the nucleotide-binding pocket.
PDB ID: 2I4IDownload
MMDB ID: 41213
PDB Deposition Date: 2006/8/22
Updated in MMDB: 2011/10
Experimental Method:
x-ray diffraction
Resolution: 2.2  Å
Source Organism:
Similar Structures:
Biological Unit for 2I4I: monomeric; determined by author
Molecular Components in 2I4I
Label Count Molecule
Protein (1 molecule)
Atp-dependent RNA Helicase Ddx3x(Gene symbol: DDX3X)
Molecule annotation
Chemical (1 molecule)
* Click molecule labels to explore molecular sequence information.

Citing MMDB