P19 complexed with 19-bp small interfering RNA

spinqualitylabelsall models 1r9f) Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image   Print3D Crystal structure of p19 complexed with 19-bp small interfering RNA (1r9f) Publication Abstract from PubMed RNA silencing (also known as RNA interference) is a conserved biological response to double-stranded RNA that regulates gene expression, and has evolved in plants as a defence against viruses. The response is mediated by small interfering RNAs (siRNAs), which guide the sequence-specific degradation of cognate messenger RNAs. As a counter-defence, many viruses encode proteins that specifically inhibit the silencing machinery. The p19 protein from the tombusvirus is such a viral suppressor of RNA silencing and has been shown to bind specifically to siRNA. Here, we report the 1.85-A crystal structure of p19 bound to a 21-nucleotide siRNA, where the 19-base-pair RNA duplex is cradled within the concave face of a continuous eight-stranded beta-sheet, formed across the p19 homodimer interface. Direct and water-mediated intermolecular contacts are restricted to the backbone phosphates and sugar 2'-OH groups, consistent with sequence-independent p19-siRNA recognition. Two alpha-helical 'reading heads' project from opposite ends of the p19 homodimer and position pairs of tryptophans for stacking over the terminal base pairs, thereby measuring and bracketing both ends of the siRNA duplex. Our structure provides an illustration of siRNA sequestering by a viral protein. Recognition of small interfering RNA by a viral suppressor of RNA silencing., Ye K, Malinina L, Patel DJ, Nature. 2003 Dec 18;426(6968):874-8. Epub 2003 Dec 3. PMID:14661029 From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. About this Structure 1R9F is a 3 chains structure of sequences from Tomato bushy stunt virus. The February 2008 RCSB PDB Molecule of the Month feature on Small Interfering RNA by David S. Goodsell is 10.2210/rcsb_pdb/mom_2008_2. Full crystallographic information is available from OCA. The structure of a homologous protein from a different plant virus (1rpu) is used in an entry detailing the structural basis of Plant Viral Protein p19 suppression of RNA Silencing. The homologous structure is covered under the topic of Suppression of RNA Silencing by Viruses.

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