The reductive half-reaction of two bifurcating electron-transferring flavoproteins: Evidence for changes in flavin reduction potentials mediated by specific conformational changes
| Autor: | Vigil, Wayne, Tran, Jessica, Niks, Dimitri, Schut, Gerrit J, Ge, Xiaoxuan, Adams, Michael WW, Hille, Russ |
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| Rok vydání: | 2022 |
| Předmět: |
Protein Structure
Biochemistry & Molecular Biology Electron-Transferring Flavoproteins electron-transferring flavoprotein Biological Sciences NAD Medical and Health Sciences Electron Transport electron paramagnetic resonance Flavins electron bifurcation Chemical Sciences Flavin-Adenine Dinucleotide Ferredoxins Oxidoreductases Oxidation-Reduction Tertiary rapid-reaction kinetics |
| Zdroj: | The Journal of biological chemistry, vol 298, iss 6 |
| Popis: | 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. |
| Databáze: | OpenAIRE |
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