Nucleic Acids Research, 1988, Vol. 16, No. 11 5013-5030
© 1988
Articles |
Bulge-out structures in the single-stranded trimer AUA and in the duplex (CUGGUGCGG).(CCGCCCAG). A model-building and NMR study
Gorlaeus Laboratories, Leiden University PO Box 9502, 2300 RA Leiden, The Netherlands
Received April 14, 1988. Accepted May 6, 1988.
Model-building studies were carried out on the trimer AUA. Bulge-out structures which allow incorporation into a continuous RNA helix were generated and energy-minimized. All geometrical features obtained by previous NMR studies on purine-pyrimidine-purine sequences are accounted for in these models. One of the models was used to fit into a double helical fragment. Only minor changes were necessary to construct a central bulge-out in an otherwise intact duplex.
NMR and model-building studies were performed on the duplex (CUGGUGCGG)·(CCGCCCAG) which contains an unpaired uridine residue. NOE data, chemical-shift profiles and imino-proton resonances provided evidence that the extra U is bulged out of the duplex. The relatively small dispersion in 31P chemical shifts (
0.7 ppm) indicate the absence of t/g or g/t combinations for the phosphodiester angles
/
. An energy-minimized model of the duplex, which fits the present collection of data, is presented.