title: Joining the two domains of a group I ribozyme to form the catalytic core.
abstract: Self-splicing group I introns, like other large catalytic RNAs, contain structural domains. Although the crystal structure of one of these domains has been determined by x-ray analysis, its connection to the other major domain that contains the guanosine-binding site has not been known. Site-directed mutagenesis and kinetic analysis of RNA splicing were used to identify a base triple in the conserved core of both a cyanobacterial (Anabaena) and a eukaryotic (Tetrahymena) group I intron. This long-range interaction connects a sequence adjacent to the guanosine-binding site with the domain implicated in coordinating the 5' splice site helix, and it thereby contributes to formation of the active site. The resulting five-strand junction, in which a short helix forms base triples with three separate strands in the Tetrahymena intron, reveals exceptionally dense packing of RNA.
authors.affiliation: Department of Chemistry and Biochemistry, Howard Hughes Medical Institute, University of Colorado, Boulder, Colorado 80309-0215, USA.
authors.forename: M A
authors.initials: MA
authors.lastname: Tanner
authors.forename: T R
authors.initials: TR
authors.lastname: Cech
mesh_terms: D017033:Anabaena / Q000235:genetics; D000818:Animals; D001482:Base Composition; D001665:Binding Sites; D006151:Guanosine / Q000378:metabolism; D007438:Introns; D016297:Mutagenesis, Site-Directed; D009690:Nucleic Acid Conformation; D012326:RNA Splicing; D012329:RNA, Bacterial / Q000235:genetics; D016337:RNA, Catalytic / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D016053:RNA, Protozoan / Q000235:genetics; D013768:Tetrahymena / Q000235:genetics
chemical_list: D012329:RNA, Bacterial; D016337:RNA, Catalytic; D016053:RNA, Protozoan; D006151:Guanosine