title: Monovalent cations mediate formation of native tertiary structure of the Tetrahymena thermophila ribozyme.
abstract: The formation of individual tertiary contacts of the Tetrahymena L-21 Sca I ribozyme has been monitored by hydroxyl radical footprinting and its global conformation by analytical ultracentrifugation as a function of monovalent ion concentration in the absence of divalent ions. Advanced methods of data analysis, which allow the hydroxyl radical reactivity of every nucleotide to be quantified, permit monitoring of each and every structural element of the RNA. Monovalent ion-mediated global compaction of the ribozyme is accompanied by the formation of native tertiary contacts; most native tertiary contacts are evident except several that are located near where divalent ions are observed in crystallographic structures. Non-native tertiary contacts are also observed at low but not high concentrations of monovalent ions. In light of recent studies that have shown that the presence of monovalent ions greatly accelerates the Mg2+-dependent folding of the Tetrahymena ribozyme, the present studies suggest that Na+ concentration changes not only the starting position of the RNA on its folding funnel but also pushes it deep into the well by forming native tertiary contacts and, thus, favoring fast and correct folding pathways.
authors.affiliation: Department of Physiology and Biophysics, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, New York 10461, USA.
authors.forename: Keiji
authors.initials: K
authors.lastname: Takamoto
authors.forename: Qin
authors.initials: Q
authors.lastname: He
authors.forename: Stephanie
authors.initials: S
authors.lastname: Morris
authors.forename: Mark R
authors.initials: MR
authors.lastname: Chance
authors.forename: Michael
authors.initials: M
authors.lastname: Brenowitz
mesh_terms: D000818:Animals; D001483:Base Sequence; D002414:Cations, Monovalent; D017665:Hydroxyl Radical; D007700:Kinetics; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009690:Nucleic Acid Conformation; D016337:RNA, Catalytic / Q000737:chemistry*; D012265:Ribonucleotides / Q000032:analysis; D012964:Sodium / Q000494:pharmacology; D016808:Tetrahymena thermophila / Q000201:enzymology*; D014461:Ultracentrifugation
chemical_list: D002414:Cations, Monovalent; D016337:RNA, Catalytic; D012265:Ribonucleotides; D017665:Hydroxyl Radical; D012964:Sodium