The reductive half-reaction of two bifurcating electron-transferring flavoproteins: Evidence for changes in flavin reduction potentials mediated by specific conformational changes.

Autor:	Vigil W Jr; Department of Biochemistry, University of California, Riverside, California, USA., Tran J; Department of Biochemistry, University of California, Riverside, California, USA., Niks D; Department of Biochemistry, University of California, Riverside, California, USA., Schut GJ; Department of Biochemistry and Molecular Biology, University of Georgia, Athens, Georgia, USA., Ge X; Department of Biochemistry and Molecular Biology, University of Georgia, Athens, Georgia, USA., Adams MWW; Department of Biochemistry and Molecular Biology, University of Georgia, Athens, Georgia, USA., Hille R; Department of Biochemistry, University of California, Riverside, California, USA. Electronic address: russ.hille@ucr.edu.
Jazyk:	angličtina
Zdroj:	The Journal of biological chemistry [J Biol Chem] 2022 Jun; Vol. 298 (6), pp. 101927. Date of Electronic Publication: 2022 Apr 13.
DOI:	10.1016/j.jbc.2022.101927
Abstrakt:	The EtfAB components of two bifurcating flavoprotein systems, the crotonyl-CoA-dependent NADH:ferredoxin oxidoreductase from the bacterium Megasphaera elsdenii and the menaquinone-dependent NADH:ferredoxin oxidoreductase from the archaeon Pyrobaculum aerophilum, have been investigated. With both proteins, we find that removal of the electron-transferring flavin adenine dinucleotide (FAD) moiety from both proteins results in an uncrossing of the reduction potentials of the remaining bifurcating FAD; this significantly stabilizes the otherwise very unstable semiquinone state, which accumulates over the course of reductive titrations with sodium dithionite. Furthermore, reduction of both EtfABs depleted of their electron-transferring FAD by NADH was monophasic with a hyperbolic dependence of reaction rate on the concentration of NADH. On the other hand, NADH reduction of the replete proteins containing the electron-transferring FAD was multiphasic, consisting of a fast phase comparable to that seen with the depleted proteins followed by an intermediate phase that involves significant accumulation of FAD⋅ - , again reflecting uncrossing of the half-potentials of the bifurcating FAD. This is then followed by a slow phase that represents the slow reduction of the electron-transferring FAD to FADH - , with reduction of the now fully reoxidized bifurcating FAD by a second equivalent of NADH. We suggest that the crossing and uncrossing of the reduction half-potentials of the bifurcating FAD is due to specific conformational changes that have been structurally characterized. Competing Interests: Conflict of interest The authors declare that they have no conflicts of interest with the contents of this article. (Copyright © 2022 The Authors. Published by Elsevier Inc. All rights reserved.)
Databáze:	MEDLINE
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