Structure of an RNA double helix including uracil-uracil base pairs in an internal loop

Nat Struct Biol. 1995 Jan;2(1):56-62. doi: 10.1038/nsb0195-56.


The crystal structure of the RNA dodecamer 5'-GGACUUUGGUCC-3' has been determined from X-ray diffraction data to 2.6 A resolution. This oligomer forms an asymmetric double helix in the crystal. Four consecutive non-Watson-Crick base-pairs are formed in the middle of the duplex including the first intrahelical U-U (or T-T) pairs observed in an oligonucleotide crystal structure. Two different conformations of U-U pairs are observed in the context of the surrounding sequence. One of these pairs is highly twisted, allowing a bound water to bridge across strands in the major groove. The crystal packing illustrates a new form of RNA helix-helix interaction.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Base Composition*
  • Base Sequence
  • Crystallography, X-Ray
  • DNA Repair
  • Hydrogen Bonding
  • Models, Molecular
  • Molecular Sequence Data
  • Nucleic Acid Conformation*
  • Oligoribonucleotides / chemistry*
  • RNA, Double-Stranded / chemistry*
  • Uracil / chemistry*
  • Water / chemistry


  • Oligoribonucleotides
  • RNA, Double-Stranded
  • Water
  • Uracil