TY  - JOUR
A1  - Bertsch, Johannes
A1  - Parthasarathy, Anutthaman
A1  - Buckel, Wolfgang
A1  - Müller, Volker
T1  - An electron-bifurcating caffeyl-CoA reductase
T2  - Journal of biological chemistry
N2  - A low potential electron carrier ferredoxin (E0′ ≈ −500 mV) is used to fuel the only bioenergetic coupling site, a sodium-motive ferredoxin:NAD+ oxidoreductase (Rnf) in the acetogenic bacterium Acetobacterium woodii. Because ferredoxin reduction with physiological electron donors is highly endergonic, it must be coupled to an exergonic reaction. One candidate is NADH-dependent caffeyl-CoA reduction. We have purified a complex from A. woodii that contains a caffeyl-CoA reductase and an electron transfer flavoprotein. The enzyme contains three subunits encoded by the carCDE genes and is predicted to have, in addition to FAD, two [4Fe-4S] clusters as cofactor, which is consistent with the experimental determination of 4 mol of FAD, 9 mol of iron, and 9 mol of acid-labile sulfur. The enzyme complex catalyzed caffeyl-CoA-dependent oxidation of reduced methyl viologen. With NADH as donor, it catalyzed caffeyl-CoA reduction, but this reaction was highly stimulated by the addition of ferredoxin. Spectroscopic analyses revealed that ferredoxin and caffeyl-CoA were reduced simultaneously, and a stoichiometry of 1.3:1 was determined. Apparently, the caffeyl-CoA reductase-Etf complex of A. woodii uses the novel mechanism of flavin-dependent electron bifurcation to drive the endergonic ferredoxin reduction with NADH as reductant by coupling it to the exergonic NADH-dependent reduction of caffeyl-CoA.
KW  - Bioenergetics
KW  - Electron Transfer
KW  - Enzyme Mechanisms
KW  - Iron-Sulfur Protein
KW  - Metalloenzymes
KW  - Acetogenesis
KW  - Electron Bifurcation
KW  - Energy Conservation
Y1  - 2021
UR  - http://publikationen.ub.uni-frankfurt.de/frontdoor/index/index/docId/76876
UR  - https://nbn-resolving.org/urn:nbn:de:hebis:30:3-768769
SN  - 0021-9258
VL  - 288
IS  - 16
SP  - 11304
EP  - 11311
PB  - American Society for Biochemistry and Molecular Biology Publications
CY  - Bethesda, Md
ER  -