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Nat Struct Mol Biol. 2011 Mar;18(3):270-6. doi: 10.1038/nsmb.1984. Epub 2011 Feb 6.

Structural and biochemical studies of the 5'→3' exoribonuclease Xrn1.

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Department of Biological Sciences, Columbia University, New York, NY, USA.


The 5'→3' exoribonucleases (XRNs) have important functions in transcription, RNA metabolism and RNA interference. The structure of Rat1 (also known as Xrn2) showed that the two highly conserved regions of XRNs form a single, large domain that defines the active site of the enzyme. Xrn1 has a 510-residue segment after the conserved regions that is required for activity but is absent from Rat1/Xrn2. Here we report the crystal structures of Kluyveromyces lactis Xrn1 (residues 1-1,245, E178Q mutant), alone and in complex with a Mn(2+) ion in the active site. The 510-residue segment contains four domains (D1-D4), located far from the active site. Our mutagenesis and biochemical studies show that their functional importance results from their ability to stabilize the conformation of the N-terminal segment of Xrn1. These domains might also constitute a platform that interacts with protein partners of Xrn1.

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