TOWARD A DESCRIPTION OF THE CONFORMATIONS OF DENATURED STATES OF PROTEINS - COMPARISON OF A RANDOM COIL MODEL WITH NMR MEASUREMENTS

A strategy is proposed to describe the backbone conformations sampled in denatured states of proteins. Main chain dihedral angle distributio ns are extracted from the protein data base and used to predict NMR pa rameters such as coupling constants and NOE intensities. A simple mode l in which each residue samples its phi, psi distribution noncooperati vely has been found to reproduce many of the features of experimental NMR data for hen egg-white lysozyme denatured in 8 M urea at low pH. T his model provides a framework which allows identification of residual structure inherent in experimental data of nonnative states of protei ns. The effects of introducing local conformational cooperativity on N MR parameters are discussed and analyzed in light of the experimental data for lysozyme.