title: Tertiary contacts distant from the active site prime a ribozyme for catalysis.
abstract: Minimal hammerhead ribozymes have been characterized extensively by static and time-resolved crystallography as well as numerous biochemical analyses, leading to mutually contradictory mechanistic explanations for catalysis. We present the 2.2 A resolution crystal structure of a full-length Schistosoma mansoni hammerhead ribozyme that permits us to explain the structural basis for its 1000-fold catalytic enhancement. The full-length hammerhead structure reveals how tertiary interactions occurring remotely from the active site prime this ribozyme for catalysis. G-12 and G-8 are positioned consistent with their previously suggested roles in acid-base catalysis, the nucleophile is aligned with a scissile phosphate positioned proximal to the A-9 phosphate, and previously unexplained roles of other conserved nucleotides become apparent within the context of a distinctly new fold that nonetheless accommodates the previous structural studies. These interactions permit us to explain the previously irreconcilable sets of experimental results in a unified, consistent, and unambiguous manner.
authors.affiliation: Department of Molecular, Cellular and Developmental Biology, Robert L. Sinsheimer Laboratories, University of California, Santa Cruz, Santa Cruz, CA 95064, USA.
authors.forename: Monika
authors.initials: M
authors.lastname: Martick
authors.forename: William G
authors.initials: WG
authors.lastname: Scott
mesh_terms: D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D002384:Catalysis; D018360:Crystallography, X-Ray; D006860:Hydrogen Bonding; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009690:Nucleic Acid Conformation; D010710:Phosphates / Q000737:chemistry / Q000378:metabolism; D016337:RNA, Catalytic / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D012550:Schistosoma mansoni / Q000201:enzymology
chemical_list: D010710:Phosphates; D016337:RNA, Catalytic; C427204:hammerhead ribozyme