title: NMR structure of an alpha-L-LNA:RNA hybrid: structural implications for RNase H recognition.
abstract: Alpha-L-LNA (alpha-L-ribo configured locked nucleic acid) is a nucleotide analogue that raises the thermostability of nucleic acid duplexes by up to approximately 4 degrees C per inclusion. We have determined the NMR structure of a nonamer alpha-L-LNA:RNA hybrid with three alpha-L-LNA modifications. The geometry of this hybrid is intermediate between A- and B-type, all nucleobases partake in Watson-Crick base pairing and base stacking, and the global structure is very similar to that of the corresponding unmodified hybrid. The sugar-phosphate backbone is rearranged in the vicinity of the modified nucleotides. As a consequence, the phosphate groups following the modified nucleotides are rotated into the minor groove. It is interesting that the alpha-L-LNA:RNA hybrid, which has an elevation in melting temperature of 17 degrees C relative to the corresponding DNA:RNA hybrid, retains the global structure of this hybrid. To our knowledge, this is the first example of such a substantial increase in melting temperature of a nucleic acid analogue that does not act as an N-type (RNA) mimic. alpha-L-LNA:RNA hybrids are recognised by RNase H with subsequent cleavage of the RNA strand, albeit with slow rates. We attempt to rationalise this impaired enzyme activity from the rearrangement of the sugar-phosphate backbone of the alpha-L-LNA:RNA hybrid.
authors.affiliation: Nucleic Acid Center, Department of Chemistry, University of Southern Denmark, 5230 Odense M, Denmark.
authors.forename: Jakob T
authors.initials: JT
authors.lastname: Nielsen
authors.forename: Paul C
authors.initials: PC
authors.lastname: Stein
authors.forename: Michael
authors.initials: M
authors.lastname: Petersen
mesh_terms: D001483:Base Sequence; D004247:DNA / Q000737:chemistry* / Q000235:genetics; D009682:Magnetic Resonance Spectroscopy / Q000379:methods; D008958:Models, Molecular; D015394:Molecular Structure; D009690:Nucleic Acid Conformation; D009692:Nucleic Acid Heteroduplexes / Q000737:chemistry* / Q000378:metabolism; D012313:RNA / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D016914:Ribonuclease H / Q000378:metabolism
chemical_list: D009692:Nucleic Acid Heteroduplexes; D012313:RNA; D004247:DNA; D016914:Ribonuclease H