4L2I

Electron transferring flavoprotein of Acidaminococcus fermentans: Towards a mechanism of flavin-based electron bifurcation

Summary for 4L2I

• Entry DOI: 10.2210/pdb4l2i/pdb
• Related: 4KPU 4L1F
• Descriptor: Electron transfer flavoprotein alpha subunit, Electron transfer flavoprotein alpha/beta-subunit, FLAVIN-ADENINE DINUCLEOTIDE, ... (6 entities in total)
• Functional Keywords: fad, electron transferring flavoprotein (etf), butyryl-coa dehydrogenase, ferredoxin, nadh, electron transport
• Biological source: Acidaminococcus fermentans; More
• Total number of polymer chains: 2
• Total formula weight: 68631.07

Authors

Mowafy, A.M.,Chowdhury, N.P.,Demmer, J.,Upadhyay, V.,Kolzer, S.,Jayamani, E.,Kahnt, J.,Demmer, U.,Ermler, U.,Buckel, W. (deposition date: 2013-06-04, release date: 2014-01-15, Last modification date: 2024-02-28)

Primary citation

Chowdhury, N.P.,Mowafy, A.M.,Demmer, J.K.,Upadhyay, V.,Koelzer, S.,Jayamani, E.,Kahnt, J.,Hornung, M.,Demmer, U.,Ermler, U.,Buckel, W.
Studies on the Mechanism of Electron Bifurcation Catalyzed by Electron Transferring Flavoprotein (Etf) and Butyryl-CoA Dehydrogenase (Bcd) of Acidaminococcus fermentans.
J.Biol.Chem., 289:5145-5157, 2014

PubMed 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 (β-FAD) in subunit β. The distance between the two isoalloxazine rings is 18 Å. The EtfAf-NAD(+) complex structure revealed β-FAD as acceptor of the hydride of NADH. The formed β-FADH(-) is considered as the bifurcating electron donor. As a result of a domain movement, α-FAD is able to approach β-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, β-FADH(•), immediately reduces ferredoxin. Repetition of this process affords a second reduced ferredoxin and Dh-FADH(-) that converts crotonyl-CoA to butyryl-CoA.

PubMed: 24379410
DOI: 10.1074/jbc.M113.521013

Experimental method

X-RAY DIFFRACTION (1.45 Å)