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A Ferredoxin Disulfide Reductase Delivers Electronsto the Methanosarcina barkeri Class III RibonucleotideReductase

View Article: PubMed Central - PubMed

ABSTRACT

Twosubtypes of class III anaerobic ribonucleotide reductases (RNRs)studied so far couple the reduction of ribonucleotides to the oxidationof formate, or the oxidation of NADPH via thioredoxin and thioredoxinreductase. Certain methanogenic archaea contain a phylogeneticallydistinct third subtype of class III RNR, with distinct active-siteresidues. Here we report the cloning and recombinant expression ofthe Methanosarcina barkeri class III RNR and showthat the electrons required for ribonucleotide reduction can be deliveredby a [4Fe-4S] protein ferredoxin disulfide reductase, and a conservedthioredoxin-like protein NrdH present in the RNR operon. The diversityof class III RNRs reflects the diversity of electron carriers usedin anaerobic metabolism.

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Pathways for methanogenesis from methanol or acetate. (A) In methylotrophicmethanogenesis, oxidation of each methyl group produces four electronsin the form of F420H2 from the oxidation ofmethyl- and methylene-tetrahydromethanopterin (H4MPT) andtwo electrons in the form of reduced Fdx from the oxidation of theformyl group to CO2 by formylmethanofuran dehydrogenase(FMF-DH). (B) In aceticlastic methanogenesis, breakdown of each acetatemolecule produces two electrons in the form of reduced Fdx from thecarbon monoxide dehydrogenase/acetyl CoA synthase system (CODH/ACS).53
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fig5: Pathways for methanogenesis from methanol or acetate. (A) In methylotrophicmethanogenesis, oxidation of each methyl group produces four electronsin the form of F420H2 from the oxidation ofmethyl- and methylene-tetrahydromethanopterin (H4MPT) andtwo electrons in the form of reduced Fdx from the oxidation of theformyl group to CO2 by formylmethanofuran dehydrogenase(FMF-DH). (B) In aceticlastic methanogenesis, breakdown of each acetatemolecule produces two electrons in the form of reduced Fdx from thecarbon monoxide dehydrogenase/acetyl CoA synthase system (CODH/ACS).53

Mentions: M. barkeri and other organisms in the order Methanosarcinalescan generate methane from methanol or methylamines [methylotrophicmethanogenesis (Figure 5A)] or from acetate [aceticlastic methanogenesis (Figure 5B)]. These pathways differin the electron carriers used in energy conservation (Figure 5), allowing us to examine thedistribution of class III RNRs among the metabolically diverse Methanosarcinalesfor clues regarding the source of electrons for reduction of NrdH(Table 3).


A Ferredoxin Disulfide Reductase Delivers Electronsto the Methanosarcina barkeri Class III RibonucleotideReductase
Pathways for methanogenesis from methanol or acetate. (A) In methylotrophicmethanogenesis, oxidation of each methyl group produces four electronsin the form of F420H2 from the oxidation ofmethyl- and methylene-tetrahydromethanopterin (H4MPT) andtwo electrons in the form of reduced Fdx from the oxidation of theformyl group to CO2 by formylmethanofuran dehydrogenase(FMF-DH). (B) In aceticlastic methanogenesis, breakdown of each acetatemolecule produces two electrons in the form of reduced Fdx from thecarbon monoxide dehydrogenase/acetyl CoA synthase system (CODH/ACS).53
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4697749&req=5

fig5: Pathways for methanogenesis from methanol or acetate. (A) In methylotrophicmethanogenesis, oxidation of each methyl group produces four electronsin the form of F420H2 from the oxidation ofmethyl- and methylene-tetrahydromethanopterin (H4MPT) andtwo electrons in the form of reduced Fdx from the oxidation of theformyl group to CO2 by formylmethanofuran dehydrogenase(FMF-DH). (B) In aceticlastic methanogenesis, breakdown of each acetatemolecule produces two electrons in the form of reduced Fdx from thecarbon monoxide dehydrogenase/acetyl CoA synthase system (CODH/ACS).53
Mentions: M. barkeri and other organisms in the order Methanosarcinalescan generate methane from methanol or methylamines [methylotrophicmethanogenesis (Figure 5A)] or from acetate [aceticlastic methanogenesis (Figure 5B)]. These pathways differin the electron carriers used in energy conservation (Figure 5), allowing us to examine thedistribution of class III RNRs among the metabolically diverse Methanosarcinalesfor clues regarding the source of electrons for reduction of NrdH(Table 3).

View Article: PubMed Central - PubMed

ABSTRACT

Twosubtypes of class III anaerobic ribonucleotide reductases (RNRs)studied so far couple the reduction of ribonucleotides to the oxidationof formate, or the oxidation of NADPH via thioredoxin and thioredoxinreductase. Certain methanogenic archaea contain a phylogeneticallydistinct third subtype of class III RNR, with distinct active-siteresidues. Here we report the cloning and recombinant expression ofthe Methanosarcina barkeri class III RNR and showthat the electrons required for ribonucleotide reduction can be deliveredby a [4Fe-4S] protein ferredoxin disulfide reductase, and a conservedthioredoxin-like protein NrdH present in the RNR operon. The diversityof class III RNRs reflects the diversity of electron carriers usedin anaerobic metabolism.

No MeSH data available.


Related in: MedlinePlus