Nucleic Acids Research, Vol 27, Issue 10 2196-2201, Copyright © 1999 by Oxford University Press
K Shi, M Wahl and M Sundaralingam
The crystal structure of a self-complementary RNA duplex r(GGGCGCUCC)2with
non-adjacent G*U and U*G wobble pairs separated by four Watson-Crick base
pairs has been determined to 2.5 A resolution. Crystals belong to the space
group R3; a = 33.09 A,alpha = 87.30 degrees with a pseudodyad related
duplex in the asymmetric unit. The structure was refined to a final Rworkof
17.5% and Rfreeof 24.0%. The duplexes stack head-to-tail forming infinite
columns with virtually no twist at the junction steps. The 3'-terminal
cytosine nucleosides are disordered and there are no electron densities,
but the 3' penultimate phosphates are observed. As expected, the wobble
pairs are displaced with guanine towards the minor groove and uracil
towards the major groove. The largest twist angles (37.70 and 40.57 degrees
) are at steps G1*C17/G2*U16 and U7*G11/C8*G10, while the smallest twist
angles (28.24 and 27.27 degrees ) are at G2*U16/G3*C15 and C6*G12/U7*G11
and conform to the pseudo-dyad symmetry of the duplex. The molecule has two
unequal kinks (17 and 11 degrees ) at the wobble sites and a third kink at
the central G5 site which may be attributed to trans alpha (O5'-P), trans
gamma (C4'-C5') backbone conformations. The 2'-hydroxyl groups in the minor
groove form inter-column hydrogen bonding, either directly or through water
molecules.
ARTICLES
Crystal structure of an RNA duplex r(G GCGC CC)2 with non-adjacent G*U base pairs
The Ohio State University, Biological Macromolecular Structure Center, Department of Chemistry, 012 Rightmire Hall, 1060 Carmack Road, Columbus, OH 43210, USA.
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