Studies on the mechanism of electron bifurcation catalyzed by electron transferring flavoprotein (Etf) and butyryl-CoA dehydrogenase (Bcd) of Acidaminococcus fermentans.
J Biol Chem
; 289(8): 5145-57, 2014 Feb 21.
Article
em En
| MEDLINE
| ID: mdl-24379410
ABSTRACT
Electron bifurcation is a fundamental strategy of energy coupling originally discovered in the Q-cycle of many organisms. Recently a flavin-based electron bifurcation has been detected in anaerobes, first in clostridia and later in acetogens and methanogens. It enables anaerobic bacteria and archaea to reduce the low-potential [4Fe-4S] clusters of ferredoxin, which increases the efficiency of the substrate level and electron transport phosphorylations. Here we characterize the bifurcating electron transferring flavoprotein (EtfAf) and butyryl-CoA dehydrogenase (BcdAf) of Acidaminococcus fermentans, which couple the exergonic reduction of crotonyl-CoA to butyryl-CoA to the endergonic reduction of ferredoxin both with NADH. EtfAf contains one FAD (α-FAD) in subunit α and a second FAD (ß-FAD) in subunit ß. The distance between the two isoalloxazine rings is 18 Å. The EtfAf-NAD(+) complex structure revealed ß-FAD as acceptor of the hydride of NADH. The formed ß-FADH(-) is considered as the bifurcating electron donor. As a result of a domain movement, α-FAD is able to approach ß-FADH(-) by about 4 Å and to take up one electron yielding a stable anionic semiquinone, α-FAD, which donates this electron further to Dh-FAD of BcdAf after a second domain movement. The remaining non-stabilized neutral semiquinone, ß-FADH(â¢), immediately reduces ferredoxin. Repetition of this process affords a second reduced ferredoxin and Dh-FADH(-) that converts crotonyl-CoA to butyryl-CoA.
Palavras-chave
Texto completo:
1
Base de dados:
MEDLINE
Assunto principal:
Acidaminococcus
/
Flavoproteínas Transferidoras de Elétrons
/
Butiril-CoA Desidrogenase
/
Elétrons
/
Biocatálise
Idioma:
En
Ano de publicação:
2014
Tipo de documento:
Article