Abstract
A decapeptide corresponding to the C-terminal sequence (residues 115-124) of bovine pancreatic ribonuclease A (RNase A) and four analogs in which Asp-121 is replaced by Asn, Glu, Gln and Ala were synthesized by the fragment condensation procedure, and their abilities to reactivate RNase A from which the last 4 residues, Asp-Ala-Ser-Val, had been removed were examined. Asp-decapeptide (I) and Glu-decapeptide (III) bound with inactivated RNase 1-120 non-covalently and exhibited hydrolytic activity towards cyclic 2', 3'-cytidylic acid. In contrast, Asn-decapeptide (II), Gln-decapeptide (IV) and Ala-decapeptide (V) did not show any ability to restore the activity of RNase A 1-120. Our systematic syntheses of the C-terminal decapeptide of RNase A and its analogs indicate a very important role of the free carboxyl group at position 121 of RNase A for manifestation of RNase activity.
