Comparison of NMR structural and dynamics features of the urea and guanidine-denatured states of GED

Denatured states of proteins, the starting points as well as the intermediates of folding in vivo, play important roles in biological function. In this context, we describe here urea unfolding and characterization of the denatured state of GTPase effector domain (GED) of dynamin created by 9.7 M urea. These are compared with similar data for guanidine induced denaturation reported earlier. The unfolding characteristics in the two cases, as measured by the optical probes, are significantly different, urea unfolding proceeding via an intermediate. The structural and motional characteristics, determined by NMR, of the two denatured states are also strikingly different. The urea-denatured state shows a combination of α- and β-preferences in contrast to the entirely β-preferences in the guanidine-denatured state. Higher 15N transverse relaxation rates suggest higher folding propensities in the urea-denatured state. The implications of these to GED folding are discussed.