Structure-based analysis of protein dynamics: Comparison of theoretical results for hen lysozyme with X-ray diffraction and NMR relaxation data

An analytical approach based on Gaussian network model (GNM) is proposed fo r predicting the rotational dynamics of proteins. The method, previously sh own to successfully reproduce X-ray crystallographic temperature factors fo r a series of proteins is extended here to predict bond torsional mobilitie s and reorientation of main chain amide groups probed by N-15-H nuclear mag netic resonance (NMR) relaxation, The dynamics of hen egg-white lysozyme (H EWL) in the folded state is investigated using the proposed approach. Excel lent agreement is observed between theoretical results and experimental (X- ray diffraction and NMR relaxation) data. The analysis reveals the importan t role of coupled rotations, or cross-correlations between dihedral angle L ibrations, in defining the relaxation mechanism on a local scale. The cryst al and solution structures exhibit some differences in their local motions, but their global motions are identical. Hinge residues mediating the coope rative movements of the alpha- and beta-domains are identified, which compr ise residues in helix C, Glu35 and Ser36 on the loop succeeding helix B, Il e55 and Leu56 at the turn between strands II and III. The central part of t he beta-domain long loop and the turn between strands I and II display an e nhanced mobility. Finally, kinetically hot residues and key interactions ar e identified, which point at helix B and beta-strand III as the structural elements underlying the stability of the tertiary structure, Proteins 1999; 37:654-667, (C) 1999 Wiley-Liss, Inc.