title: Structural and biochemical studies of the 5'→3' exoribonuclease Xrn1.
abstract: 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.
authors.affiliation: Department of Biological Sciences, Columbia University, New York, NY, USA.
authors.forename: Jeong Ho
authors.initials: JH
authors.lastname: Chang
authors.forename: Song
authors.initials: S
authors.lastname: Xiang
authors.forename: Kehui
authors.initials: K
authors.lastname: Xiang
authors.forename: James L
authors.initials: JL
authors.lastname: Manley
authors.forename: Liang
authors.initials: L
authors.lastname: Tong
mesh_terms: D020134:Catalytic Domain; D005095:Exoribonucleases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D007716:Kluyveromyces / Q000737:chemistry / Q000201:enzymology* / Q000235:genetics / Q000378:metabolism; D008345:Manganese / Q000737:chemistry / Q000378:metabolism*; D008958:Models, Molecular; D009154:Mutation; D017434:Protein Structure, Tertiary
chemical_list: D008345:Manganese; D005095:Exoribonucleases