PROTEIN-FOLDING MONITORED AT INDIVIDUAL RESIDUES DURING A 2-DIMENSIONAL NMR EXPERIMENT

An approach is described to monitor directly at the level of individua l residues the formation of structure during protein folding. A two-di mensional heteronuclear nuclear magnetic resonance (NMR) spectrum was recorded after the rapid initiation of the refolding of a protein labe led with nitrogen-15. The intensities and line shapes of the cross pea ks in the spectrum reflected the kinetic time course of the folding ev ents that occurred during the spectral accumulation. The method was us ed to demonstrate the cooperative nature of the acquisition of the nat ive main chain fold of apo bovine alpha-lactalbumin. The general appro ach, however, should be applicable to the investigation of a wide rang e of chemical reactions.