The ribonucleotide reductase system of Lactococcus lactis: Characterization of an NrdEF enzyme and a new electron transport protein

Albert Jordan, Elisabet Pontis, Fredrik Åslund, Ulf Hellman, Isidre Gibert, Peter Reichard

Research output: Contribution to journalArticleResearchpeer-review

87 Citations (Scopus)

Abstract

Escherichia coli contains the genetic information for three separate ribonucleotide reductases. Two of them (class I enzymes), coded by the nrdAB and nrdEF genes, respectively, contain a tyrosyl radical, whose generation requires oxygen. The NrdAB enzyme is physiologically active. The function of the nrdEF gene is not known. The third enzyme (class III), coded by nrdDG, operates during anaerobiosis. The DNA of Lactococcus lactis contains sequences homologous to the nrdDG genes. Surprisingly, an nrdD- mutant of L. lactis grew well under standard anaerobic growth conditions. The ribonucleotide reductase system of this mutant was shown to consist of an enzyme of the NrdEF-type and a small electron transport protein. The coding operon contains the nrdEF genes and two open reading frames, one of which (nrdH) codes for the small protein. The same gene organization is present in E. coli. We propose that the aerobic class I ribonucleotide reductases contain two subclasses, one coded by nrdAB, active in E. coli and eukaryotes (class Ia), the other coded by nrdEF, present in various microorganisms (class Ib). The Nr-dEF enzymes use NrdH proteins as electron transporter in place of thioredoxin or glutaredoxin used by NrdAB enzymes. The two classes also differ in their allosteric regulation by dATP.
Original languageEnglish
Pages (from-to)8779-8785
JournalJournal of Biological Chemistry
Volume271
Issue number15
DOIs
Publication statusPublished - 12 Apr 1996

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