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Electron Bifurcation and Confurcation in Methanogenesis and Reverse Methanogenesis
1Department of Biochemistry and Molecular Biology, Pennsylvania State University, State College, PA, United States.
Frontiers in Microbiology
|July 6, 2018
Summary
Heterodisulfide reductases (HdrED and HdrABC) are key in methanogenesis. Flavin-based electron bifurcation by HdrABC drives essential reactions, enabling energy conservation across diverse methanogenic pathways.
Area of Science:
- Biochemistry
- Microbiology
- Bioenergetics
Background:
- The final step in methanogenesis involves heterodisulfide reductase (HdrED and HdrABC) catalyzing the reduction of coenzyme M and coenzyme B disulfide (CoMS-SCoB).
- Flavin-based electron bifurcation (FBEB) is a critical mechanism employed by soluble HdrABC homologs to drive endergonic reactions.
- FBEB utilizes the exergonic reduction of CoMS-SCoB to power other essential cellular processes.
Purpose of the Study:
- To elucidate the diverse roles of HdrABC complexes in various methanogenic pathways.
- To explain how FBEB and related mechanisms facilitate energy conservation in methanogenesis.
- To detail the involvement of HdrABC in CO2 reduction, methanol and acetate metabolism, and reverse methanogenesis.
Main Methods:
- Analysis of biochemical pathways involving heterodisulfide reductases (HdrED, HdrABC).
- Investigation of flavin-based electron bifurcation (FBEB) and flavin-based electron confurcation (FBEC) mechanisms.
- Characterization of electron transfer processes involving ferredoxin (Fdx) and coenzyme F420.
Main Results:
- HdrABC complexes, often with hydrogenase or formate dehydrogenase, facilitate CO2 reduction via FBEB, coupling it to CoMS-SCoB reduction.
- In H2-independent pathways, HdrABC and related complexes mediate methyl group reduction using Fdx and F420, with FBEB driving endergonic steps.
- HdrABC complexes are implicated in acetotrophic and reverse methanogenesis, involving electron transfer with Fdx, F420, and membrane complexes like Rnf.
Conclusions:
- HdrABC complexes are central to methanogenesis, utilizing FBEB to drive crucial endergonic reactions across diverse substrates.
- The intricate interplay of HdrABC, Fdx, and F420 enables efficient energy conservation in both forward and reverse methanogenic pathways.
- Understanding these mechanisms provides insights into microbial energy metabolism and potential biotechnological applications.
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