Simultaneous determination of protein backbone structure and dynamics from residual dipolar couplings.

Determination of protein structure classically results in a single average configuration that takes no account of conformational fluctuation. Dynamics are, however, inherently linked to structure and crucial to our understanding of biological function. In this study we have used analytical descriptions of dynamic averaging of residual dipolar couplings (RDCs) to simultaneously determine the backbone structure and dynamics of protein GB3. RDCs alone are used to determine an ultrahigh-resolution structure that compares very closely with a refined X-ray structure (rmsd of 0.34 A overall backbone residues). Dynamic amplitudes reporting on motions up to the millisecond time scale reproduce the main characteristics of dynamics previously determined in conjunction with the crystal structure. The use of RDCs alone allows a bias-free comparison with a purely static approach to structure determination. Extensive cross validation clearly demonstrates that the dynamic description is superior to the static approximation. The demonstration that this level of structural resolution and dynamic detail can be extracted from RDCs supports previous indications that these parameters contain extremely precise information about biomolecular conformational sampling.