Refinement of the structure of protein-RNA complexes by residual dipolar coupling analysis

The main limitation in NMR-determined structures of nucleic acids and their complexes with proteins derives from the elongated, non-globular nature of physiologically important DNA and RNA molecules. Since it is generally not possible to obtain long-range distance constraints between distinct region s of the structure, long-range properties such as bending or kinking at sit es of protein recognition cannot be determined accurately nor precisely. He re we show that use of residual dipolar couplings in the refinement of the structure of a protein-RNA complex improves the definition of the long-rang e properties of the RNA. These features are often an important aspect of mo lecular recognition and biological function; therefore, their improved defi nition is of significant value in RNA structural biology.