Intermolecular Interactions and Protein Dynamics by Solid-State NMR Spectroscopy.

Understanding the dynamics of interacting proteins is a crucial step toward describing many biophysical processes. Here we investigate the backbone dynamics for protein GB1 in two different assemblies: crystalline GB1 and the precipitated GB1–antibody complex with a molecular weight of more than 300 kDa. We perform these measurements on samples containing as little as eight nanomoles of GB1. From measurements of site-specific 15N relaxation rates including relaxation dispersion we obtain snapshots of dynamics spanning nine orders of magnitude in terms of the time scale. A comparison of measurements for GB1 in either environment reveals that while many of the dynamic features of the protein are conserved between them (in particular for the fast picosecond–nanosecond motions), much greater differences occur for slow motions with motions in the >500 ns range being more prevalent in the complex. The data suggest that GB1 can potentially undergo a small-amplitude overall anisotropic motion sampling the interaction interface in the complex.