Biophysical Journal
Volume 97, Issue 9, 4 November 2009, Pages 2513-2520
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Article
Analysis of Sub-τc and Supra-τc Motions in Protein Gβ1 Using Molecular Dynamics Simulations

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Abstract

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 Gβ1, we analyzed molecular dynamics simulations with the model-free approach of nuclear magnetic relaxation. We found amplitudes of fast timescale motions (sub-τc, where τc is the rotational correlation time) consistent with S2 obtained from spin relaxation measurements as well as amplitudes of slow timescale motions (supra-τc) in quantitative agreement with S2 order parameters derived from residual dipolar coupling measurements. The slow timescale motions are associated with the large variations of the 3J 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.

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Jennifer M. Bui and Jörg Gsponer contributed equally to this work.