CRYSTAL-STRUCTURES OF A SERIES OF RNA APTAMERS COMPLEXED TO THE SAME PROTEIN TARGET

We have determined the crystal structures, at 2.8 Angstrom resolution, of two different RNA aptamers, each bound to MS2 coat protein. One of the aptamers contains a non-Watson-Crick base pair, while the other i s missing one of the unpaired adenines that make sequence-specific con tacts in the wild-type complex, Despite these differences, the RNA apt amers bind in the same location on the protein as the wild-type transl ational operator. Comparison of these new structures with other MS2-RN A complexes allows us to refine further the definition of the minimal recognition elements and suggests a possible application of the MS2 sy stem for routine structure determination of small nucleic acid motifs.