Coupling of ferredoxin and heterodisulfide reduction via electron bifurcation in hydrogenotrophic methanogenic archaea
Abstract
In methanogenic archaea growing on H2 and CO2 the first step in methanogenesis is the ferredoxin-dependent endergonic reduction of CO2 with H2 to formylmethanofuran and the last step is the exergonic reduction of the heterodisulfide CoM-S-S-CoB with H2 to coenzyme M (CoM-SH) and coenzyme B (CoB-SH). We recently proposed that in hydrogenotrophic methanogens the two reactions are energetically coupled via the cytoplasmic MvhADG/HdrABC complex. It is reported here that the purified complex from Methanothermobacter marburgensis catalyzes the CoM-S-S-CoB-dependent reduction of ferredoxin with H2. Per mole CoM-S-S-CoB added, 1 mol of ferredoxin (Fd) was reduced, indicating an electron bifurcation coupling mechanism: ? This stoichiometry of coupling is consistent with an ATP gain per mole methane from 4 H2 and CO2 of near 0.5 deduced from an H2-threshold concentration of 8 Pa and a growth yield of up to 3 g/mol methane.
- Publication:
-
Proceedings of the National Academy of Science
- Pub Date:
- February 2011
- DOI:
- 10.1073/pnas.1016761108
- Bibcode:
- 2011PNAS..108.2981K