Thiol‐Disulfide Exchange Kinetics and Redox Potential of the Coenzyme M and Coenzyme B Heterodisulfide, an Electron Acceptor Coupled to Energy Conservation in Methanogenic Archaea

Maxime Gabriel Laird, Norman Adlung, Jari J Koivisto, Silvan Scheller (Corresponding Author)

Research output: Contribution to journalArticleScientificpeer-review

Abstract

Methanogenic and methanotrophic archaea play important roles in the global carbon cycle by interconverting CO2 and methane. To conserve energy from these metabolic pathways that happen close to the thermodynamic equilibrium, specific electron carriers have evolved to balance the redox potentials between key steps. Reduced ferredoxins required to activate CO2 are provided by energetical coupling to the reduction of the high‐potential heterodisulfide (HDS) of coenzyme M (2‐mercaptoethanesulfonate) and coenzyme B (7‐mercaptoheptanoylthreonine phosphate).While the standard redox potential of this important HDS has been determined previously to be ‐143 mV (Tietze et al. 2003 DOI:10.1002/cbic.200390053), we have measured thiol disulfide exchange kinetics and reassessed this value by equilibrating thiol‐disulfide mixtures of coenzyme M, coenzyme B and mercaptoethanol. We determined the redox potential of the HDS of coenzyme M and coenzyme B to be ‐16.4 ± 1.7 mV relative to the reference thiol mercaptoethanol (E0’ = ‐264 mV). The resulting E0’ values are ‐281 mV for the HDS, ‐271 mV for the homodisulfide of coenzyme M, and ‐270 mV for the homodisulfide of coenzyme B. We discuss the importance of these updated values for the physiology of methanogenic and methanotrophic archaea and their implications in terms of energy conservation.
Original languageEnglish
Article numbere202300595
JournalChemBioChem
Volume25
Issue number1
DOIs
Publication statusPublished - 2 Jan 2024
MoE publication typeA1 Journal article-refereed

Funding

. This work made use of Aalto University Raw Materials Research Infrastructures and Bioeconomy facilities. We thank the Novo Nordisk Foundation (grant NNF19OC0054329 to S. S. and NNF19OC0055464 to N.A.) and the Academy of Finland (grant 326020 to S. S.) for funding this research. We thank other group members for helpful comments and suggestions on the manuscript

Keywords

  • cofactors
  • heterodisulfide
  • kinetics
  • methanogenesis
  • NMR spectroscopy
  • redox potentials

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