Coupling of ferredoxin and heterodisulfide reduction via electron bifurcation in hydrogenotrophic methanogenic archaea.
Proc Natl Acad Sci U S A
; 108(7): 2981-6, 2011 Feb 15.
Article
em En
| MEDLINE
| ID: mdl-21262829
ABSTRACT
In methanogenic archaea growing on H(2) and CO(2) the first step in methanogenesis is the ferredoxin-dependent endergonic reduction of CO(2) with H(2) to formylmethanofuran and the last step is the exergonic reduction of the heterodisulfide CoM-S-S-CoB with H(2) 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 H(2). Per mole CoM-S-S-CoB added, 1 mol of ferredoxin (Fd) was reduced, indicating an electron bifurcation coupling mechanism 2H(2) + Fd(OX) + CoM-S-S-CoB-->Fd(red)(2-) + CoM-SH + CoB-SH + 2H(+). This stoichiometry of coupling is consistent with an ATP gain per mole methane from 4 H(2) and CO(2) of near 0.5 deduced from an H(2)-threshold concentration of 8 Pa and a growth yield of up to 3 g/mol methane.
Texto completo:
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Base de dados:
MEDLINE
Assunto principal:
Dióxido de Carbono
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Methanobacteriaceae
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Dissulfetos
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Ferredoxinas
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Hidrogênio
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Metano
Idioma:
En
Ano de publicação:
2011
Tipo de documento:
Article