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-Structure paper
タイトル | Cryoelectron microscopy structure and mechanism of the membrane-associated electron-bifurcating flavoprotein Fix/EtfABCX. |
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ジャーナル・号・ページ | Proc Natl Acad Sci U S A, Vol. 118, Issue 2, Year 2021 |
掲載日 | 2021年1月12日 |
![]() | Xiang Feng / Gerrit J Schut / Gina L Lipscomb / Huilin Li / Michael W W Adams / ![]() |
PubMed 要旨 | 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 ...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. |
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手法 | EM (単粒子) |
解像度 | 2.9 Å |
構造データ | EMDB-22973, PDB-7koe: |
化合物 | ![]() ChemComp-FAD: ![]() ChemComp-MQ7: ![]() ChemComp-SF4: |
由来 |
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![]() | FLAVOPROTEIN/Oxidoreductase / membrane-associated / flavin based electron bifurcation / FLAVOPROTEIN / FLAVOPROTEIN-Oxidoreductase complex |