title: RNA splicing: group I intron crystal structures reveal the basis of splice site selection and metal ion catalysis.
abstract: The group I intron has served as a model for RNA catalysis since its discovery 25 years ago. Four recently determined high-resolution crystal structures complement extensive biochemical studies on this system. Structures of the Azoarcus, Tetrahymena and bacteriophage Twort group I introns mimic different states of the splicing or ribozyme reaction pathway and provide information on splice site selection and metal ion catalysis. The 5'-splice site is selected by formation of a conserved G.U wobble pair between the 5'-exon terminus and the intron. The 3'-splice site is identified through stacking of three base triples, in which the middle triple contains the conserved terminal nucleotide of the intron, OmegaG. The structures support a two-metal-ion mechanism for group I intron splicing that might have corollaries to group II intron and pre-mRNA splicing by the spliceosome.
authors.affiliation: Department of Molecular Biophysics and Biochemistry, Yale University, 260 Whitney Avenue, New Haven, CT 06520-8114, USA.
authors.forename: Mary R
authors.initials: MR
authors.lastname: Stahley
authors.forename: Scott A
authors.initials: SA
authors.lastname: Strobel
mesh_terms: D001665:Binding Sites; D002384:Catalysis; D007438:Introns; D007477:Ions; D008670:Metals / Q000378:metabolism*; D008958:Models, Molecular; D009690:Nucleic Acid Conformation; D012313:RNA / Q000737:chemistry* / Q000378:metabolism; D012326:RNA Splicing
chemical_list: D007477:Ions; D008670:Metals; D012313:RNA