Measurement of barnase refolding rate constants under denaturing conditions

Calculation of equilibrium and kinetic constants between the different species that occur in the folding pathway of a protein usually depends on extrapolations from conditions where these quantities can be accurately measured. Direct measurements of the extrapolated constants would allow the checking of the validity of the extrapolations. We measure here refolding constants of barnase under unfolding conditions by displacing the folding equilibrium by complexing folded barnase with its polypeptide inhibitor barstar. Formation of the enzyme-inhibitor complex is very fast and virtually irreversible, and so refolding rate constants can be obtained. The results acquired confirm the extrapolations carried out in previous works.