7KOE
Electron bifurcating flavoprotein Fix/EtfABCX
Summary for 7KOE
| Entry DOI | 10.2210/pdb7koe/pdb |
| EMDB information | 22973 |
| Descriptor | Electron transfer flavoprotein, beta subunit, Electron transfer flavoprotein, alpha subunit, Electron transfer flavoprotein-quinone oxidoreductase FixC, ... (7 entities in total) |
| Functional Keywords | membrane-associated, flavin based electron bifurcation, flavoprotein, flavoprotein-oxidoreductase complex, flavoprotein/oxidoreductase |
| Biological source | Thermotoga maritima (strain ATCC 43589 / MSB8 / DSM 3109 / JCM 10099) More |
| Total number of polymer chains | 8 |
| Total formula weight | 266571.27 |
| Authors | |
| Primary citation | Feng, X.,Schut, G.J.,Lipscomb, G.L.,Li, H.,Adams, M.W.W. Cryoelectron microscopy structure and mechanism of the membrane-associated electron-bifurcating flavoprotein Fix/EtfABCX. Proc.Natl.Acad.Sci.USA, 118:-, 2021 Cited by PubMed Abstract: The electron-transferring flavoprotein-menaquinone oxidoreductase ABCX (EtfABCX), also known as FixABCX for its role in nitrogen-fixing organisms, is a member of a family of electron-transferring flavoproteins that catalyze electron bifurcation. EtfABCX enables endergonic reduction of ferredoxin (°' ∼-450 mV) using NADH (°' -320 mV) as the electron donor by coupling this reaction to the exergonic reduction of menaquinone (°' -80 mV). Here we report the 2.9 Å structure of EtfABCX, a membrane-associated flavin-based electron bifurcation (FBEB) complex, from a thermophilic bacterium. EtfABCX forms a superdimer with two membrane-associated EtfCs at the dimer interface that contain two bound menaquinones. The structure reveals that, in contrast to previous predictions, the low-potential electrons bifurcated from EtfAB are most likely directly transferred to ferredoxin, while high-potential electrons reduce the quinone via two [4Fe-4S] clusters in EtfX. Surprisingly, EtfX shares remarkable structural similarity with mammalian [4Fe-4S] cluster-containing ETF ubiquinone oxidoreductase (ETF-QO), suggesting an unexpected evolutionary link between bifurcating and nonbifurcating systems. Based on this structure and spectroscopic studies of a closely related EtfABCX, we propose a detailed mechanism of the catalytic cycle and the accompanying structural changes in this membrane-associated FBEB system. PubMed: 33372143DOI: 10.1073/pnas.2016978118 PDB entries with the same primary citation |
| Experimental method | ELECTRON MICROSCOPY (2.9 Å) |
Structure validation
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