2'-Azido-2'-deoxynucleotide interaction with E. coli ribonucleotide reductase: generation of a new radical species

• Published in: Journal of the American Chemical Society 1984-03, Vol.106 (6), p.1886-1887
• Main Authors: Ator, M, Salowe, S. P, Stubbe, J, Emptage, M. H, Robins, M. J
• Format: Article
• Language: English
• Subjects: 2'-azido-2'-deoxynucleotide; Escherichia coli; radicals; ribonucleoside-diphosphate reductase
• ISSN: 0002-7863; 1520-5126
• DOI: 10.1021/ja00318a082

Ribonucleotide reductase (RDPR) from E. coli catalyzes the conversion of nucleoside diphospahtes to deoxynucleoside diphosphates. This enzyme is composed of two subunits: B sub(1) ( alpha , alpha ' M sub(r) 160,000) binds NDP substrates and contains redox active thiols and binding sites for the allosteric effectors; B sub(2) ( beta , beta M sub(r) 78,000) contains an unusual cofactor composed of two Fe super(+3) and one tyrosine radical, which is an integral part of the B sub(2) polypeptide chain. The authors report findings with specifically labeled substrate analogues (2'- super(2)H)N sub(3)UDP super(1) and (2'- super(15)N)N sub(3)UDP. The results clearly indicate formation of the same radical species as observed by Sjoeberg et al. Results with the (2'- super(15)N)N sub(3)UDP and (2'- super(2)N)N sub(3)UDP indicate that the new radical is indeed located on a nitrogen originally at the 2'-position of the substrate and that the observed coupling of this species to hydrogen is not caused by the hydrogen on the 2-carbon. Structures proposed by Sjoeberg et al. for this radical are inconsistent with the results.