Renaturation of soluble and immobilized ribonuclease: are the polypeptide folding pathways for structure formation the same for soluble proteins and for proteins associated with a surface?

Abstract

During the refolding and oxidation of reductively denatured ribonuclease A in solution, there is a marked lag in appearance of enzymatic activity as compared to the oxidation of sulfhydryl groups, whether such oxidation is spontaneous or is catalyzed by sulfhydryl oxidase. However, if ribonuclease is covalently attached to a derivatized glass surface, a lag period is not observed during the reformation of native structure from the completely reduced, denatured state. These results suggest that, in solution, intermolecular interactions alter the pathway of polypeptide chain folding and disulfide bond formation, leading to nonnative disulfides which do not rapidly interchange to form native pairings. The isolation of refolding polypeptide chains by covalent immobilization prevents such interactions. Presumably, such intermolecular interactions would be similarly prevented by "isolation" of nascent polypeptide chains during protein synthesis on ribosomes.