Thiyl radicals in ribonucleotide reductases

Stuart Licht, Gary J. Gerfen, Joanne Stubbe

Research output: Contribution to journalArticle

253 Scopus citations

Abstract

The ribonucleoside triphosphate reductase (RTPR) from Lactobacillus leichmannii catalyzes adenosylcobalamin (AdoCbl)-dependent nucleotide reduction, as well as exchange of the 5' hydrogens of AdoCbl with solvent. A protein-based thiyl radical is proposed as an intermediate in both of these processes. In the presence of RTPR containing specifically deuterated cysteine residues, the electron paramagnetic resonance (EPR) spectrum of an intermediate in the exchange reaction and the reduction reaction, trapped by rapid freeze quench techniques, exhibits narrowed hyperfine features relative to the corresponding unlabeled RTPR. The spectrum was interpreted to represent a thiyl radical coupled to cob(II)alamin. Another proposed intermediate, 5'-deoxyadenosine, was detected by rapid acid quench techniques. Similarities in mechanism between RTPR and the Escherichia coli ribonucleotide reductase suggest that both enzymes require a thiyl radical for catalysis.

Original languageEnglish (US)
Pages (from-to)477-481
Number of pages5
JournalScience
Volume271
Issue number5248
DOIs
StatePublished - Jan 26 1996
Externally publishedYes

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