Analysis of sub-tauc and supra-tauc motions in protein Gbeta1 using molecular dynamics simulations.

The functions of proteins depend on the dynamical behavior of their native states on a wide range of timescales. To investigate these dynamics in the case of the small protein Gbeta1, we analyzed molecular dynamics simulations with the model-free approach of nuclear magnetic relaxation. We found amplitudes of fast timescale motions (sub-tau(c), where tau(c) is the rotational correlation time) consistent with S(2) obtained from spin relaxation measurements as well as amplitudes of slow timescale motions (supra-tau(c)) in quantitative agreement with S(2) order parameters derived from residual dipolar coupling measurements. The slow timescale motions are associated with the large variations of the (3)J couplings that follow transitions between different conformational substates. These results provide further characterization of the large structural fluctuations in the native states of proteins that occur on timescales longer than the rotational correlation time.