Unfolding and refolding of the N-terminal fragments of staphylococcal nuclease R in guanidine hydrochloride

The conformational and activity changes of a family of peptide fragments of staphylococcal nuclease R, which extend from residues -6 to 102, -6 to 110, -6 to 121, -6 to 135, and -6 to 141, during unfolding and refolding in different concentrations of guanidine hydrochloride have been studied, The studies indicate that the conformational stability in guanidine hydrochloride solution of the N-terminal fragment increases with increasing chain length, and that interaction and recognition between amino acid residues which are related to formation of the native conformation also increase with growth of the peptide chain, but such interaction becomes effective only when the polypeptide chain reaches a certain length, The changes in conformation and catalytic activity of the N-terminal fragments during unfolding and refolding demonstrate that conformational adjustments are necessary during chain elongation to generate the native conformation of a biologically active protein.