The carboxyl terminus heptapeptide of the R2 subunit of mammalian ribonucleotide reductase inhibits enzyme activity and can be used to purify the R1 subunit

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Abstract
The heptapeptide, FTLDADF, identical in sequence to the last seven amino acid residues of the carboxyl terminus of the R2 subunit of mouse ribonucleotide reductase (RR), and its Nα-acetyl derivative both inhibit calf thymus RR. The Nα-acetyl derivative is considerably more potent, displaying a K i of 20 μM. The same K i was found for N-AcFTLDADF inhibition of a reconstituted ribonucleotide reductase from calf thymus R1 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 R1, devoid of contamination with R2, in a very simple procedure that should be generally applicable to Rl purification from many sources.