title: In-line alignment and Mg²⁺ coordination at the cleavage site of the env22 twister ribozyme.
abstract: Small self-cleaving nucleolytic ribozymes contain catalytic domains that accelerate site-specific cleavage/ligation of phosphodiester backbones. We report on the 2.9-Å crystal structure of the env22 twister ribozyme, which adopts a compact tertiary fold stabilized by co-helical stacking, double-pseudoknot formation and long-range pairing interactions. The U-A cleavage site adopts a splayed-apart conformation with the modelled 2'-O of U positioned for in-line attack on the adjacent to-be-cleaved P-O5' bond. Both an invariant guanosine and a Mg(2+) are directly coordinated to the non-bridging phosphate oxygens at the U-A cleavage step, with the former positioned to contribute to catalysis and the latter to structural integrity. The impact of key mutations on cleavage activity identified an invariant guanosine that contributes to catalysis. Our structure of the in-line aligned env22 twister ribozyme is compared with two recently reported twister ribozymes structures, which adopt similar global folds, but differ in conformational features around the cleavage site.
authors.affiliation: Structural Biology Program, Memorial Sloan-Kettering Cancer Center, New York, New York 10065, USA.
authors.forename: Aiming
authors.initials: A
authors.lastname: Ren
authors.affiliation: Institute of Organic Chemistry, Leopold-Franzens University and Center of Molecular Biosciences Innsbruck CMBI, Innsbruck A-6020, Austria.
authors.forename: Marija
authors.initials: M
authors.lastname: Košutić
authors.affiliation: Department of Chemistry and Chemical Biology, Cornell University, NE-CAT, Advanced Photon Source, Argonne National laboratory, Argonne, Illinois 60439, USA.
authors.forename: Kanagalaghatta R
authors.initials: KR
authors.lastname: Rajashankar
authors.affiliation: Institute of Organic Chemistry, Leopold-Franzens University and Center of Molecular Biosciences Innsbruck CMBI, Innsbruck A-6020, Austria.
authors.forename: Marina
authors.initials: M
authors.lastname: Frener
authors.affiliation: Institute of Organic Chemistry, Leopold-Franzens University and Center of Molecular Biosciences Innsbruck CMBI, Innsbruck A-6020, Austria.
authors.forename: Tobias
authors.initials: T
authors.lastname: Santner
authors.affiliation: Architecture et Réactivité de l'ARN, Institute of Molecular and Cellular Biology, University of Strasbourg, CNRS, Strasbourg F-67084, France.
authors.forename: Eric
authors.initials: E
authors.lastname: Westhof
authors.affiliation: Institute of Organic Chemistry, Leopold-Franzens University and Center of Molecular Biosciences Innsbruck CMBI, Innsbruck A-6020, Austria.
authors.forename: Ronald
authors.initials: R
authors.lastname: Micura
authors.affiliation: Structural Biology Program, Memorial Sloan-Kettering Cancer Center, New York, New York 10065, USA.
authors.forename: Dinshaw J
authors.initials: DJ
authors.lastname: Patel
mesh_terms: D002413:Cations, Divalent; D018360:Crystallography, X-Ray; D008274:Magnesium; D009690:Nucleic Acid Conformation; D016337:RNA, Catalytic
chemical_list: D002413:Cations, Divalent; D016337:RNA, Catalytic; D008274:Magnesium