DEAD-box RNA-helicase DDX19 in complex with ADP

spinqualitylabelsall models Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image   Print3D Human DEAD-box RNA-helicase DDX19 in complex with ADP (3ews) Publication Abstract from PubMed DEXD/H-box RNA helicases couple ATP hydrolysis to RNA remodeling by an unknown mechanism. We used x-ray crystallography and biochemical analysis of the human DEXD/H-box protein DDX19 to investigate its regulatory mechanism. The crystal structures of DDX19, in its RNA-bound prehydrolysis and free posthydrolysis state, reveal an alpha-helix that inserts between the conserved domains of the free protein to negatively regulate ATPase activity. This finding was corroborated by biochemical data that confirm an autoregulatory function of the N-terminal region of the protein. This is the first study describing crystal structures of a DEXD/H-box protein in its open and closed cleft conformations. The DEXD/H-box RNA helicase DDX19 is regulated by an {alpha}-helical switch., Collins R, Karlberg T, Lehtio L, Schutz P, van den Berg S, Dahlgren LG, Hammarstrom M, Weigelt J, Schuler H, J Biol Chem. 2009 Apr 17;284(16):10296-300. Epub 2009 Feb 25. PMID:19244245 From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. About this Structure 3EWS is a 2 chains structure of sequences from Homo sapiens. Full crystallographic information is available from OCA. The crystallographic asymmetric unit of the solved structure contains 2 monomers of DDX19 (residues 53-472 of 479 for both molecules) complexed with the nucleotide ADP. The biological molecule is a single-chain DDX19 monomer. . DDX19 is made of 2 RecA-like helicase domains (called the N-terminal ATPase and C-terminal helicase domains in the paper). With ADP bound, an N-terminal extension (dark green) is wedged in a cleft between these domains negatively regulating ATPase activity by preventing cleft closure. This conformation is presumed to resemble the post-hydrolysis state in which RNA is not bound. It is also referred to as the open state and open cleft conformation. This scene is similar to the view in Figure 1a of the paper describing the structure. (This scene is even more similar because Arginine 429, discussed below, is included as in that figure.) Showing the structure of DDX19 with ADP bound along with the structure where RNA and an ATP analog are bound. This overlay clearly illustrates the dramatic shift in the location of the N-terminal extension (dark green). This view clearly shows how the N-terminal helix of the extension extends from the RNA-binding site to down near the ATP binding site. Pre-hydrolysis (RNA and ATP bound) to post-hydrolysis (ADP bound) morph. The placement of the N-terminal extension between the two helicase domains negatively regulates ATPase activity. A morph of the ADP-bound structure transitioning to the structure with a non-hydrolyzable ATP analog and mRNA mimic bound shows the N-terminal extension moving out of the way, closing the cleft to allow formation of a functional ATPase site. Of particular note is arginine 429, the so-called arginine finger, that is essential for ATPase activity. In the ADP bound structure arginine 429 is far from the nucleotide-binding site due to the helix of the extension sitting in the cleft. Watching arginine 429 during the morph transition illustrates how it is moved to sit near the active site when RNA is bound, enabling ATPase activity. Keep in mind the intermediate models, in between the endpoints, are hypothetical. See also Helicase 3g0h is human DDX19 with a non-hydrolyzable ATP analog and mRNA mimic bound. It is used in the morphs here and was described in the same article as 3ews.

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