Structure of an RNA double helix including uracil-uracil base pairs in an internal loop.
Baeyens, K.J., De Bondt, H.L., Holbrook, S.R.(1995) Nat Struct Biol 2: 56-62
- PubMed: 7719854 
- DOI: https://doi.org/10.1038/nsb0195-56
- Primary Citation of Related Structures:  
205D - PubMed Abstract: 
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.
Organizational Affiliation: 
Structural Biology Division, Lawrence Berkeley Laboratory, University of California, Berkeley 94720.