Effect of prolyl isomerase on the folding reactions of staphylococcal nuclease

Three slow kinetic phases describe the low-temperature fluorescence-detected refolding of staphylococcal nuclease (SNase). Peptidyl prolyl cis-trans isomerase, which is proven to catalyze the slow folding reactions of some proteins, was used in determining which of the refolding reactions of SNase and P117G SNase involve proline isomerization. Results support the hypothesis that the slow folding steps involve isomerization of non-native cis proline peptide bonds are are tightly coupled to denaturant-sensitive structural changes.