Cited by 169Redox biology and oxidative stressGlutathione Transferases and PolymorphismsMetal-Catalyzed Oxygenation Mechanisms

Molecular Mechanisms of Thioredoxin and Glutaredoxin as Hydrogen Donors for Mammalian S Phase Ribonucleotide Reductase

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Avval, Farnaz Zahedi, Holmgren, Arne·2009·Journal of Biological Chemistry

Abstract

Ribonucleotide reductase (RNR) catalyzes the rate-limiting step in deoxyribonucleotide synthesis essential for DNA replication and repair. RNR in S phase mammalian cells comprises a weak cytosolic complex of the catalytic R1 protein containing redox active cysteine residues and the R2 protein harboring the tyrosine free radical. Each enzyme turnover generates a disulfide in the active site of R1, which is reduced by C-terminally located shuttle dithiols leaving a disulfide to be reduced. Electrons for reduction come ultimately from NADPH via thioredoxin reductase and thioredoxin (Trx) or glutathione reductase, glutathione, and glutaredoxin (Grx), but the mechanism has not been clarified for mammalian RNR. Using recombinant mouse RNR, we found that Trx1 and Grx1 had similar catalytic efficiency (k(cat)/K(m)). With 4 mm GSH, Grx1 showed a higher affinity (apparent K(m) value, 0.18 microm) compared with Trx1 which displayed a higher apparent k(cat), suggesting its major role in S phase DNA replication. Surprisingly, Grx activity was strongly dependent on GSH concentrations (apparent K(m) value, 3 mm) and a Grx2 C40S mutant was active despite only one cysteine residue in the active site. This demonstrates a GSH-mixed disulfide mechanism for glutaredoxin catalysis in contrast to the dithiol mechanism for thioredoxin. This may be an advantage with the low levels of RNR for DNA repair or in tumor cells with high RNR and no or low Trx expression. Our results demonstrate mechanistic differences between the mammalian and canonical Escherichia coli RNR enzymes, which may offer an explanation for the nonconserved shuttle dithiol sequences in the C terminus of the R1.

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Crossref · 10.1074/jbc.m809338200

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Authors
Avval, F. Z., & Holmgren, A.
Affiliations
Karolinska Institutet (SE)
Corresponding author
Holmgren, Arne
Venue
Journal of Biological Chemistry
Publisher
Elsevier BV
Published
2009-03
Volume
284
Issue
13
Pages
8233-8240
ISSN
0021-9258 (ISSN-L)
OpenAlex
W2095557093
Cited by
169
References
62
Citations by year
2026: 7 · 2025: 5 · 2024: 10 · 2023: 6 · 2022: 10 · 2021: 13 · 2020: 7 · 2019: 6 · 2018: 11 · 2017: 12 · 2016: 9 · 2015: 7 · 2014: 9 · 2013: 5 · 2012: 11
FWCI
6.92
Type
journal article
Language
en
Open access
Locations
  • Journal of Biological Chemistry (publishedVersion, cc-by)
  • PubMed Central (publishedVersion)
  • PubMed (publishedVersion)
Topics
  • Life Sciences › Biochemistry, Genetics and Molecular Biology › Molecular Biology › Redox biology and oxidative stress
  • Life Sciences › Biochemistry, Genetics and Molecular Biology › Molecular Biology › Glutathione Transferases and Polymorphisms
  • Physical Sciences › Chemistry › Inorganic Chemistry › Metal-Catalyzed Oxygenation Mechanisms
Keywords
ribonucleotide reductase, thioredoxin, glutaredoxin, glutathione, disulfide bond reduction, hydrogen donors, NADPH, DNA repair, cancer cells, enzyme kinetics
MeSH terms
Animals, Catalysis, Deoxyribonucleotides, DNA Replication, Escherichia coli, Hydrogen, Ribonucleotide Reductases, Thioredoxins, S Phase, Catalytic Domain, Escherichia coli Proteins, Mice, Glutaredoxins

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