title: Exceptionally fast self-cleavage by a Neurospora Varkud satellite ribozyme.
abstract: Most of the small ribozymes, including those that have been investigated as potential therapeutic agents, appear to be rather poor catalysts. These RNAs use an internal phosphoester transfer mechanism to catalyze site-specific RNA cleavage with apparent cleavage rate constants typically <2 min(-1). We have identified variants of one of these, the Neurospora Varkud satellite ribozyme, that self-cleaves with experimentally measured apparent rate constants of up to 10 s(-1) (600 min(-1)), approximately 2 orders of magnitude faster than any previously characterized self-cleaving RNA. We describe structural features of the cleavage site loop and an adjacent helix that affect the apparent rate constants for cleavage and ligation and the equilibrium between them. These data show that the phosphoester transfer ribozymes can catalyze reactions with rate constants much larger than previously appreciated and in the range of those of protein enzymes that perform similar reactions.
authors.affiliation: Department of Molecular and Medical Genetics, University of Toronto, Toronto, Ontario, Canada M5S 1A8.
authors.forename: Ricardo
authors.initials: R
authors.lastname: Zamel
authors.forename: Alan
authors.initials: A
authors.lastname: Poon
authors.forename: Dominic
authors.initials: D
authors.lastname: Jaikaran
authors.forename: Angela
authors.initials: A
authors.lastname: Andersen
authors.forename: Joan
authors.initials: J
authors.lastname: Olive
authors.forename: Diane
authors.initials: D
authors.lastname: De Abreu
authors.forename: Richard A
authors.initials: RA
authors.lastname: Collins
mesh_terms: D001483:Base Sequence; D006868:Hydrolysis; D008969:Molecular Sequence Data; D009491:Neurospora / Q000201:enzymology / Q000235:genetics / Q000378:metabolism*; D009690:Nucleic Acid Conformation; D016337:RNA, Catalytic / Q000737:chemistry / Q000378:metabolism*
chemical_list: D016337:RNA, Catalytic