A '-form RNA double helix in the single crystal structure of r(UGAGCUUCGGCUC)

Here we demonstrate the presence of the A'-RNA conformation using the singl e crystal structure of a tridecamer: r(UGAGCUUCGGCUC). The average A'-RNA c onformation deduced from X-ray fiber diffraction data had only been availab le previously, but now the presence of the A'-RNA conformation has been fou nd in a single crystal structure for the first time. Statistical analysis s howed that the A'-RNA conformation is distinguishable from the A-RNA confor mation in a plot of the major groove width against the base pair inclinatio n angle. The major groove of the A'-RNA conformation is wide enough to acco mmodate a protein or peptide while that of the A-RNA conformation is too na rrow to do so. The presence of the A'-RNA conformation is significant for p rotein-RNA interaction.