Abstract
Two subtypes of class III anaerobic ribonucleotide reductases (RNRs) studied so far couple the reduction of ribonucleotides to the oxidation of formate, or the oxidation of NADPH via thioredoxin and thioredoxin reductase. Certain methanogenic archaea contain a phylogenetically distinct third subtype of class III RNR, with distinct active-site residues. Here we report the cloning and recombinant expression of the Methanosarcina barkeri class III RNR and show that the electrons required for ribonucleotide reduction can be delivered by a [4Fe-4S] protein ferredoxin disulfide reductase, and a conserved thioredoxin-like protein NrdH present in the RNR operon. The diversity of class III RNRs reflects the diversity of electron carriers used in anaerobic metabolism.
Publication types
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Research Support, N.I.H., Extramural
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Research Support, Non-U.S. Gov't
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Research Support, U.S. Gov't, Non-P.H.S.
MeSH terms
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Amino Acid Sequence
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Base Sequence
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Citric Acid / metabolism
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Cloning, Molecular
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Electrons
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Ferredoxins / metabolism
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Methanosarcina barkeri / chemistry
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Methanosarcina barkeri / enzymology*
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Methanosarcina barkeri / genetics
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Methanosarcina barkeri / metabolism
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Models, Molecular
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Molecular Sequence Data
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Oxidation-Reduction
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Oxidoreductases Acting on Sulfur Group Donors / metabolism*
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Phylogeny
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Recombinant Proteins / chemistry
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Recombinant Proteins / genetics
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Recombinant Proteins / metabolism
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Ribonucleotide Reductases / chemistry
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Ribonucleotide Reductases / genetics
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Ribonucleotide Reductases / metabolism*
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Ribonucleotides / metabolism
Substances
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Ferredoxins
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Recombinant Proteins
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Ribonucleotides
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Citric Acid
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Ribonucleotide Reductases
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anaerobic ribonucleotide reductase
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Oxidoreductases Acting on Sulfur Group Donors