Electron Bifurcation Makes the Puzzle Pieces Fall Energetically into Place in Methanogenic Energy Conservation.

Elaborate arrays of iron-sulfur clusters link active sites via a flavin that bifurcates electrons through two energetically independent paths. The structure of the heterodisulfide reductase provides insight into how methanogens conserve energy through coupling hydrogen oxidation to coordinated exergonic heterodisulfide and endergonic ferredoxin reduction in an overall thermodynamically favorable reaction.