The Covalent Linkage of a Viologen to a Flavoprotein Reductase Transforms it into an Oxidase

Bes, M. Teresa; Lacey, Antonio L. De; Peleato, M. Luisa; Fernández, Vı́ctor M.; Gómez‐Moreno, Carlos

doi:10.1111/j.1432-1033.1995.593_2.x

Cited by 8 publications

(7 citation statements)

References 29 publications

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“…Limited electron supply from PSI would therefore extend the lifetime of this unstable semiquinone before the second reduction, leading to increased electron donation to O 2 from the semiquinone. Production of O 2 c2 by the FAD semiquinone radical of FNR is supported by a study from Bes et al (1995), who report that while FNR is a poor electron donor to O 2 when the FAD is fully reduced by NADPH, cross-liking FNR to a viologen molecule (which as a single electron carrier would generate a semiquinone at the FAD) converts the enzyme to an efficient NADPH oxidase (Bes et al, 1995). The ratio of PSI:Fd:FNR therefore seems critical to minimize O 2 c2 production during PET.…”

Section: Increased Soluble Fnr Results In O 2 C2 Productionmentioning

confidence: 85%

Ferredoxin:NADP(H) Oxidoreductase Abundance and Location Influences Redox Poise and Stress Tolerance

Kozuleva

Goss²,

Twachtmann³

et al. 2016

Plant Physiol.

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In linear photosynthetic electron transport, ferredoxin:NADP(H) oxidoreductase (FNR) transfers electrons from ferredoxin (Fd) to NADP Both NADPH and reduced Fd (Fd) are required for reductive assimilation and light/dark activation/deactivation of enzymes. FNR is therefore a hub, connecting photosynthetic electron transport to chloroplast redox metabolism. A correlation between FNR content and tolerance to oxidative stress is well established, although the precise mechanism remains unclear. We investigated the impact of altered FNR content and localization on electron transport and superoxide radical evolution in isolated thylakoids, and probed resulting changes in redox homeostasis, expression of oxidative stress markers, and tolerance to high light in planta. Our data indicate that the ratio of Fd to FNR is critical, with either too much or too little FNR potentially leading to increased superoxide production, and perception of oxidative stress at the level of gene transcription. In FNR overexpressing plants, which show more NADP(H) and glutathione pools, improved tolerance to high-light stress indicates that disturbance of chloroplast redox poise and increased free radical generation may help "prime" the plant and induce protective mechanisms. In fnr1 knock-outs, the NADP(H) and glutathione pools are more oxidized relative to the wild type, and the photoprotective effect is absent despite perception of oxidative stress at the level of gene transcription.

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Section: Increased Soluble Fnr Results In O 2 C2 Productionmentioning

confidence: 85%

Ferredoxin:NADP(H) Oxidoreductase Abundance and Location Influences Redox Poise and Stress Tolerance

Kozuleva

Goss²,

Twachtmann³

et al. 2016

Plant Physiol.

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“…Moreover, it is worth mentioning that a special reactivity of the side chain of Glu139 has already been shown by chemical modification. 37 Glu301Ala Anabaena FNR also showed altered FAD reoxidation properties, supporting the idea that the flavin ring exposure is an important factor in the mechanism of flavoprotein reoxidation. Reoxidation of free reduced flavins has been shown to proceed via formation of C(4a)hydroperoxide intermediates.…”

Section: Discussionsupporting

confidence: 55%

Structural basis of the catalytic role of Glu301 inAnabaena PCC 7119 ferredoxin-NADP+ reductase revealed by x-ray crystallography

et al. 2000

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The three-dimensional crystal structure of the Glu301Ala site-directed mutant of ferredoxin-NADP+ reductase from Anabaena PCC 7119 has been determined at 1.8A resolution by x-ray diffraction. The overall folding of the Glu301Ala FNR mutant shows no significant differences with respect to that of the wild-type enzyme. However, interesting conformational changes are detected in the side chain of another glutamate residue, Glu139, which now points towards the FAD cofactor in the active center cavity. The new conformation of the Glu139 side chain is stabilized by a network of five hydrogen bonds to several water molecules, which seem to hold the carboxylate side chain in a rather fixed position. This interacting network connects the Glu139 side chain to the Ser80 side chain through a series of three water molecules. These observations are discussed in terms of the reactivity of Glu301Ala ferredoxin-NADP+ reductase towards its substrates, and the role of Glu301 in the catalysis is re-examined. Moreover, a structural explanation of the different reoxidation properties of this mutant is given on the basis of the reported structure by modeling the hypothetical flavin C(4a)-hydroperoxide intermediate. The model shows that the distal oxygen of the peroxide anion could be in an appropriate situation to act as the proton donor in the reoxidation process.

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“…Given the redox stoichiometry of the cyclase reaction (first requirement for two electrons, followed by removal of four electrons), it may be significant that the flavin moiety of FNR is capable of accepting two electrons (Batie and Kamin, ), and that its reduced state is a poor donor of electrons to oxygen (Bes et al ., ). There are several ways that FNR could support the cyclase reaction.…”

Section: Discussionmentioning

confidence: 97%

Potential roles of YCF54 and ferredoxin‐NADPH reductase for magnesium protoporphyrin monomethylester cyclase

et al. 2018

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Chlorophyll is synthesized from activated glutamate in the tetrapyrrole biosynthesis pathway through at least 20 different enzymatic reactions. Among these, the MgProto monomethylester (MgProtoME) cyclase catalyzes the formation of a fifth isocyclic ring to tetrapyrroles to form protochlorophyllide. The enzyme consists of two proteins. The CHL27 protein is proposed to be the catalytic component, while LCAA/YCF54 likely acts as a scaffolding factor. In comparison to other reactions of chlorophyll biosynthesis, this enzymatic step lacks clear elucidation and it is hardly understood, how electrons are delivered for the NADPH-dependent cyclization reaction. The present study intends to elucidate more precisely the role of LCAA/YCF54. Transgenic Arabidopsis lines with inactivated and overexpressed YCF54 reveal the mutual stability of YCF54 and CHL27. Among the YCF54-interacting proteins, the plastidal ferredoxin-NADPH reductase (FNR) was identified. We showed in N. tabacum and A. thaliana that a deficit of FNR1 or YCF54 caused MgProtoME accumulation, the substrate of the cyclase, and destabilization of the cyclase subunits. It is proposed that FNR serves as a potential donor for electrons required in the cyclase reaction and connects chlorophyll synthesis with photosynthetic activity.

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The Covalent Linkage of a Viologen to a Flavoprotein Reductase Transforms it into an Oxidase

Cited by 8 publications

References 29 publications

Ferredoxin:NADP(H) Oxidoreductase Abundance and Location Influences Redox Poise and Stress Tolerance

Ferredoxin:NADP(H) Oxidoreductase Abundance and Location Influences Redox Poise and Stress Tolerance

Structural basis of the catalytic role of Glu301 inAnabaena PCC 7119 ferredoxin-NADP+ reductase revealed by x-ray crystallography

Potential roles of YCF54 and ferredoxin‐NADPH reductase for magnesium protoporphyrin monomethylester cyclase

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