Correlation of folding kinetics with the number and isomerization states of prolines in three homologous proteins of the RNase family

Several studies attribute the slower phases in protein folding to prolyl isomerizations, and several others do not. A correlation exists between the number of prolines in a protein and the complexity of the mechanism with which it folds. In this study, we have demonstrated a direct correlation between the number of cis-prolyl bonds in a native protein and the complexity with which it folds via slower phases by studying the folding of three structurally homologous proteins of the ribonuclease family, namely RNase A, onconase and angiogenin, which differ in the number and isomerization states of their proline residues.