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Toward a mechanistic and physiological understanding of a ferredoxin:disulfide reductase from the domains Archaea and Bacteria.

ABSTRACT: Disulfide reductases reduce other proteins and are critically important for cellular redox signaling and homeostasis. Methanosarcina acetivorans is a methane-producing microbe from the domain Archaea that produces a ferredoxin:disulfide reductase (FDR) for which the crystal structure has been reported, yet its biochemical mechanism and physiological substrates are unknown. FDR and the extensively characterized plant-type ferredoxin:thioredoxin reductase (FTR) belong to a distinct class of disulfide reductases that contain a unique active-site [4Fe-4S] cluster. The results reported here support a mechanism for FDR similar to that reported for FTR with notable exceptions. Unlike FTR, FDR contains a rubredoxin [1Fe-0S] center postulated to mediate electron transfer from ferredoxin to the active-site [4Fe-4S] cluster. UV-visible, EPR, and Mössbauer spectroscopic data indicated that two-electron reduction of the active-site disulfide in FDR involves a one-electron-reduced [4Fe-4S]1+ intermediate previously hypothesized for FTR. Our results support a role for an active-site tyrosine in FDR that occupies the equivalent position of an essential histidine in the active site of FTR. Of note, one of seven Trxs encoded in the genome (Trx5) and methanoredoxin, a glutaredoxin-like enzyme from M. acetivorans, were reduced by FDR, advancing the physiological understanding of FDR's role in the redox metabolism of methanoarchaea. Finally, bioinformatics analyses show that FDR homologs are widespread in diverse microbes from the domain Bacteria.

SUBMITTER: Prakash D

PROVIDER: S-EPMC6005431 | biostudies-literature | 2018 Jun

REPOSITORIES: biostudies-literature

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Toward a mechanistic and physiological understanding of a ferredoxin:disulfide reductase from the domains Archaea and Bacteria.

Prakash Divya D Walters Karim A KA Martinie Ryan J RJ McCarver Addison C AC Kumar Adepu K AK Lessner Daniel J DJ Krebs Carsten C Golbeck John H JH Ferry James G JG

The Journal of biological chemistry 20180502 24

Disulfide reductases reduce other proteins and are critically important for cellular redox signaling and homeostasis. <i>Methanosarcina acetivorans</i> is a methane-producing microbe from the domain Archaea that produces a ferredoxin:disulfide reductase (FDR) for which the crystal structure has been reported, yet its biochemical mechanism and physiological substrates are unknown. FDR and the extensively characterized plant-type ferredoxin:thioredoxin reductase (FTR) belong to a distinct class of ...[more]

PMID: 29720404

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Project description:Heterodisulfide reductases (Hdr) of the HdrABC class are ancient enzymes and a component of the anaerobic core belonging to the prokaryotic common ancestor. The ancient origin is consistent with the widespread occurrence of genes encoding putative HdrABC homologs in metabolically diverse prokaryotes predicting diverse physiological functions; however, only one HdrABC has been characterized and that was from a narrow metabolic group of obligate CO2-reducing methanogenic anaerobes (methanogens) from the domain Archaea Here we report the biochemical characterization of an HdrABC homolog (HdrA2B2C2) from the acetate-utilizing methanogen Methanosarcina acetivorans with unusual properties structurally and functionally distinct from the only other HdrABC characterized. Homologs of the HdrA2B2C2 archetype are present in phylogenetically and metabolically diverse species from the domains Bacteria and Archaea The expression of the individual HdrA2, HdrB2, and HdrB2C2 enzymes in Escherichia coli, and reconstitution of an active HdrA2B2C2 complex, revealed an intersubunit electron transport pathway dependent on ferredoxin or coenzyme F420 (F420H2) as an electron donor. Remarkably, HdrA2B2C2 couples the previously unknown endergonic oxidation of F420H2 and reduction of ferredoxin with the exergonic oxidation of F420H2 and reduction of the heterodisulfide of coenzyme M and coenzyme B (CoMS-SCoB). The unique electron bifurcation predicts a role for HdrA2B2C2 in Fe(III)-dependent anaerobic methane oxidation (ANME) by M. acetivorans and uncultured species from ANME environments. HdrA2B2C2, ubiquitous in acetotrophic methanogens, was shown to participate in electron transfer during acetotrophic growth of M. acetivorans and proposed to be essential for growth in the environment when acetate is limiting. IMPORTANCE:Discovery of the archetype HdrA2B2C2 heterodisulfide reductase with categorically unique properties extends the understanding of this ancient family beyond CO2-reducing methanogens to include diverse prokaryotes from the domains Bacteria and Archaea The unprecedented coenzyme F420-dependent electron bifurcation, an emerging fundamental principle of energy conservation, predicts a role for HdrA2B2C2 in diverse metabolisms, including anaerobic CH4-oxidizing pathways. The results document an electron transport role for HdrA2B2C2 in acetate-utilizing methanogens responsible for at least two-thirds of the methane produced in Earth's biosphere. The previously unavailable heterologous production of individual subunits and the reconstitution of HdrA2B2C2 with activity have provided an understanding of intersubunit electron transfer in the HdrABC class and a platform for investigating the principles of electron bifurcation.

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Dataset Information

Toward a mechanistic and physiological understanding of a ferredoxin:disulfide reductase from the domains Archaea and Bacteria.

Publications

Toward a mechanistic and physiological understanding of a ferredoxin:disulfide reductase from the domains Archaea and Bacteria.

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