NMR spectroscopy and protein folding: studies of lysozyme and alpha-lactalbumin

The description of the folding process for any protein has as a principal objective the characterization of the structural changes that occur during the transition from a disordered state to a highly ordered state. It is now generally accepted that folding occurs via some pathway or pathways which can be described in terms of intermediate, partially folded states. Three complementary strategies have emerged for obtaining structural information about intermediate states. The first involves characterization of species generated transiently during refolding of denatured proteins, either in real time or by means of trapping experiments. The second involves the study of those partially folded states, such as the increasingly recognized molten globule state, which are stable under equilibrium conditions. The third strategy involves the design and study of peptide models of folding intermediates. NMR spectroscopy, because of its ability to provide information at the molecular level about protein structure and dynamics in solution, plays a crucial role in each of these strategies. We describe results from our own studies of lysozyme and alpha-lactalbumin to illustrate the scope and potential of NMR spectroscopy in studies of protein folding.