STRUCTURAL AND DYNAMIC CHARACTERIZATION OF PARTIALLY FOLDED STATES OFAPOMYOGLOBIN AND IMPLICATIONS FOR PROTEIN-FOLDING

The structure and dynamics of two partially folded states of apomyoglo bin have been characterized at equilibrium using multi-dimensional NMR spectroscopy. Residue-specific measurements of chemical shift and int ernal dynamics in these states and in the native apoprotein and holopr otein indicate progressive accumulation of secondary structure and inc reasing restriction of backbone dynamics as the chain collapses to for m increasingly compact states. Under weakly folding conditions, the po lypeptide fluctuates between unfolded states and local elements of str ucture that become extended and stabilized as the chain becomes more c ompact. These results provide a detailed model for molecular events th at are likely to occur during folding of myoglobin.