Long-range motional restrictions in a multidomain zinc-finger protein from anisotropic tumbling

Abstract

Structural characterization of biomolecules in solution by nuclear magnetic resonance (NMR) spectroscopy is based primarily on the use of interproton distances derived from homonuclear cross-relaxation experiments. Information about short time-scale dynamics, on the other hand, is obtained from relaxation rates of heteronuclear spin pairs such as 15N-1H. By combining the two types of data and utilizing the dependence of heteronuclear NMR relaxation rates on anisotropic diffusional rotational tumbling, it is possible to obtain structural information about long-range motional correlations between protein domains. This approach was applied to characterize the relative orientations and mobilities of the first three zinc-finger domains of the Xenopus transcription factor TFIIIA in aqueous solution. The data indicate that the motions of the individual zinc-finger domains are highly correlated on time scales shorter than 10 nanoseconds and that the average conformation of the three-finger polypeptide is elongated.