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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.

No MeSH data available.


(A)Example of PFV analysis of MbNrdH at pH 7.0 and 25 °C.The dashed line is the background capacitance of the blank workingelectrode. The solid line shows the raw data with MbNrdH on the electrode.The two reversible peaks of the inset were obtained from backgroundsubtraction. The reduction potential (Em) of MbNrdH is determined by averaging the potential values of thetwo peaks. SHE is the standard hydrogen electrode. (B) pH dependenceof the MbNrdH reduction potential at 25 °C. MbNrdH reductionpotentials at different pH values were fitted to a linear model (Em = 129.4 – 53.2 × pH unit).
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fig4: (A)Example of PFV analysis of MbNrdH at pH 7.0 and 25 °C.The dashed line is the background capacitance of the blank workingelectrode. The solid line shows the raw data with MbNrdH on the electrode.The two reversible peaks of the inset were obtained from backgroundsubtraction. The reduction potential (Em) of MbNrdH is determined by averaging the potential values of thetwo peaks. SHE is the standard hydrogen electrode. (B) pH dependenceof the MbNrdH reduction potential at 25 °C. MbNrdH reductionpotentials at different pH values were fitted to a linear model (Em = 129.4 – 53.2 × pH unit).

Mentions: All NrdD3 sequences thatwe have examined, from methanogens that have been sequenced to date,occur adjacent to a thioredoxin-like protein NrdH, making it a likelycandidate for the electron donor for NrdD3. To investigate this possibility,we conducted PFV of MbNrdH to determine its reduction potential (Figure 4A).


A Ferredoxin Disulfide Reductase Delivers Electronsto the Methanosarcina barkeri Class III RibonucleotideReductase
(A)Example of PFV analysis of MbNrdH at pH 7.0 and 25 °C.The dashed line is the background capacitance of the blank workingelectrode. The solid line shows the raw data with MbNrdH on the electrode.The two reversible peaks of the inset were obtained from backgroundsubtraction. The reduction potential (Em) of MbNrdH is determined by averaging the potential values of thetwo peaks. SHE is the standard hydrogen electrode. (B) pH dependenceof the MbNrdH reduction potential at 25 °C. MbNrdH reductionpotentials at different pH values were fitted to a linear model (Em = 129.4 – 53.2 × pH unit).
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Related In: Results  -  Collection

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fig4: (A)Example of PFV analysis of MbNrdH at pH 7.0 and 25 °C.The dashed line is the background capacitance of the blank workingelectrode. The solid line shows the raw data with MbNrdH on the electrode.The two reversible peaks of the inset were obtained from backgroundsubtraction. The reduction potential (Em) of MbNrdH is determined by averaging the potential values of thetwo peaks. SHE is the standard hydrogen electrode. (B) pH dependenceof the MbNrdH reduction potential at 25 °C. MbNrdH reductionpotentials at different pH values were fitted to a linear model (Em = 129.4 – 53.2 × pH unit).
Mentions: All NrdD3 sequences thatwe have examined, from methanogens that have been sequenced to date,occur adjacent to a thioredoxin-like protein NrdH, making it a likelycandidate for the electron donor for NrdD3. To investigate this possibility,we conducted PFV of MbNrdH to determine its reduction potential (Figure 4A).

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.