The heptapeptide, FTLDADF, identicai in sequence to the last seven amino acid residues of the carboxyl terminus of the R2 subunit of mouse ribonucleotide reductase (RR), and its NE-acetyl derivative both inhibit calf thymus RR. The Na-acetyl derivative is considerably more potent, displaying a K, of 20 PM. The same K, was found for N-AcFTLDADF inhibition of a reconstituted ribonucleotide reductase from calf thymus Rl and mouse R2, indicating that the C-termini of calf R2 and mouse R2 might be identical. Our results, taken together with previous results of others on inhibition of viral RR, suggest that inhibition of RRs by peptides mimicking the C-terminus of R2 may be a general phenomenon. In addition, we have shown that an affinity column, FTLDADF-Sepharose 4B, can be used to prepare -95% pure calf thymus Ri, devoid of contamination with R2, in a very simple procedure that should be generally applicable to Rl pu~fi~tion from many sources.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.