Structural highlights
Publication Abstract from PubMedThe electron transferring flavoprotein/butyryl-CoA dehydrogenase (EtfAB/Bcd) catalyzes the reduction of one crotonyl-CoA and two ferredoxins by two NADH within a flavin-based electron-bifurcating process. Here we report on the X-ray structure of the Clostridium difficile (EtfAB/Bcd)4 complex in the dehydrogenase-conducting D-state, alpha-FAD (bound to domain II of EtfA) and delta-FAD (bound to Bcd) being 8 A apart. Superimposing Acidaminococcus fermentans EtfAB onto C. difficile EtfAB/Bcd reveals a rotation of domain II of nearly 80 degrees . Further rotation by 10 degrees brings EtfAB into the bifurcating B-state, alpha-FAD and beta-FAD (bound to EtfB) being 14 A apart. This dual binding mode of domain II, substantiated by mutational studies, resembles findings in non-bifurcating EtfAB/acyl-CoA dehydrogenase complexes. In our proposed mechanism, NADH reduces beta-FAD, which bifurcates. One electron goes to ferredoxin and one to alpha-FAD, which swings over to reduce delta-FAD to the semiquinone. Repetition affords a second reduced ferredoxin and delta-FADH(-), which reduces crotonyl-CoA. The semiquinone swing in the bifurcating electron transferring flavoprotein/butyryl-CoA dehydrogenase complex from Clostridium difficile.,Demmer JK, Pal Chowdhury N, Selmer T, Ermler U, Buckel W Nat Commun. 2017 Nov 17;8(1):1577. doi: 10.1038/s41467-017-01746-3. PMID:29146947[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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