title: R2 C-terminal peptide inhibition of mammalian and yeast ribonucleotide reductase.
abstract: Eucaryotic ribonucleotide reductases (RR) catalyze the reduction of ribonucleoside diphosphates to 2'-deoxyribonucleoside diphosphates. Each has an R1(2)R2(2) quaternary structure with each subunit playing a critical role in catalysis. Separation of the subunits results in loss of activity. Previous studies have demonstrated that peptides corresponding to the C-terminus of R2 disrupt subunit association by competion with R2 and have potential usefulness as therapeutics. Extensive structure-function studies have been carried out on peptide inhibition of herpes simplex RR in an effort to develop antiviral agents based on the observation that the herpes simplex R2 C-terminus, YAGAVVNDL, is quite different from the corresponding mammalian sequence. In this work we report a detailed structure-function analysis of peptide inhibition of mammalian and, to a more limited extent, Saccharomyces cerevisiae RRs. Our results for mammalian RR support the following conclusions with regard to the effect of substitution on inhibitory potency: (a) the N-acetylated R2 C-terminal heptapeptide N-AcPhe384Thr385Leu386Asp387Ala388Asp389Phe390 (N-AcF7TLDADF1) is the minimal core peptide length required; deletion of the N-terminus or of middle positions (resulting in penta- and hexapeptides) results in large losses in inhibitory potency; (b) a free carboxylate is required on the C-terminal Phe; (c) Phe is strongly preferred to Leu in positions 1 and 7 and a bulky aliphatic group is preferred in position 5; (d) neither negative charge in positions 2 or 4 nor a polar side chain in position 6 are required for peptide binding, contrary to what evolutionary patterns in the R2 C-terminus of RR would suggest. S. cerevisiae RR displays a similar length dependence on the corresponding N-acetylated R2 C-terminal heptapeptide, N-AcFTFNEDF. This peptide has a 4-fold higher inhibitory potency toward S. cerevisiae RR than toward mammalian RR. Such selectivity raises the possibility that peptide analogs related to R2 C-termini can be developed as therapeutic agents even against organisms having R2 C-terminal sequences similar to that of mammalian RR.
authors.affiliation: Department of Chemistry, University of Pennsylvania, Philadelphia 19104-6323.
authors.forename: A
authors.initials: A
authors.lastname: Fisher
authors.forename: F D
authors.initials: FD
authors.lastname: Yang
authors.forename: H
authors.initials: H
authors.lastname: Rubin
authors.forename: B S
authors.initials: BS
authors.lastname: Cooperman
mesh_terms: D000107:Acetylation; D000595:Amino Acid Sequence; D000818:Animals; D002417:Cattle; D051379:Mice; D008969:Molecular Sequence Data; D009842:Oligopeptides / Q000138:chemical synthesis / Q000494:pharmacology*; D012264:Ribonucleotide Reductases / Q000037:antagonists & inhibitors*; D012441:Saccharomyces cerevisiae / Q000201:enzymology*; D013045:Species Specificity; D013329:Structure-Activity Relationship
chemical_list: D009842:Oligopeptides; D012264:Ribonucleotide Reductases