Regeneration of Activity by Mixture of Ribonuclease Enzymically Degraded from the COOH Terminus and a Synthetic COOH-terminal Tetradecapeptide

Abstract A peptide corresponding to the 14 amino acid residues at the COOH terminus of bovine pancreatic ribonuclease has been synthesized by the solid phase method. When this peptide was mixed with ribonuclease that had been inactivated by proteolytic removal of the 6 residues (-His-Phe-Asp-Ala-Ser-Val) at the COOH terminus, 90% of the activity of native RNase was regenerated toward cyclic 2',3'-cytidylic acid as substrate and 70% toward RNA at a peptide to protein ratio of 3. High activity was also regenerated when only 5 residues had been removed from RNase and moderate activity was obtained when 4 residues had been removed. No activity could be recovered when the full complement of residues was present but the molecule had been inactivated by carboxymethylation of histidine-119. It was further found that peptides representing both ends of the RNase molecule, the NH2-terminal S-peptide (1–20) and the COOH-terminal peptide (111–124), containing both of the catalytically essential histidine residues, could be bound noncovalently to an inactive core (21–118) to regenerate activity.