title: Movement of the guide sequence during RNA catalysis by a group I ribozyme.
abstract: Ribozymes derived from the self-splicing pre-ribosomal RNA of Tetrahymena act as sequence-specific endonucleases. The reaction involves binding an RNA or DNA substrate by base pairing to the internal guide sequence (IGS) to form helix P1. Site-specific photo-crosslinking localized the 5' end of the IGS in helix P1 to the vicinity of conserved bases between helices P4 and P5, supporting a major feature of the Michel-Westhof three-dimensional structure model. The crosslinked ribozyme retained catalytic activity. When not base-paired, the IGS was still specifically crosslinked, but the major site was 37 A distant from the reactive site in the experimentally supported three-dimensional model. The data indicate that a substantial induced-fit conformational change accompanies P1 formation, and they provide a physical basis for understanding the transport of oligonucleotides to the catalytic core of the ribozyme. The ability of RNA to orchestrate large-scale conformational changes may help explain why the ribosome and the spliceosome are RNA-based machines.
authors.affiliation: Howard Hughes Medical Institute, Department of Chemistry and Biochemistry, University of Colorado, Boulder 80309.
authors.forename: J F
authors.initials: JF
authors.lastname: Wang
authors.forename: W D
authors.initials: WD
authors.lastname: Downs
authors.forename: T R
authors.initials: TR
authors.lastname: Cech
mesh_terms: D000818:Animals; D001482:Base Composition; D001483:Base Sequence; D001665:Binding Sites; D002384:Catalysis; D004247:DNA / Q000737:chemistry / Q000378:metabolism; D008969:Molecular Sequence Data; D009690:Nucleic Acid Conformation; D009843:Oligoribonucleotides / Q000737:chemistry / Q000378:metabolism; D012313:RNA / Q000737:chemistry / Q000378:metabolism*; D016337:RNA, Catalytic / Q000737:chemistry / Q000378:metabolism*; D016053:RNA, Protozoan / Q000737:chemistry / Q000378:metabolism; D013768:Tetrahymena / Q000201:enzymology; D058727:RNA, Small Untranslated
chemical_list: D009843:Oligoribonucleotides; D016337:RNA, Catalytic; D016053:RNA, Protozoan; D012313:RNA; D004247:DNA; D058727:RNA, Small Untranslated