Electron Transfer from the Rieske Iron-Sulfur Protein (ISP) to Cytochrome f in Vitro

Soriano, Glenda M.; Guo, Lian‐Wang; Vitry, Catherine de; Kallas, Toivo; Cramer, William A.

doi:10.1074/jbc.m205772200

Cited by 25 publications

(14 citation statements)

References 50 publications

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“…10 times slower than the reaction between cytochrome f and plastocyanin [43], the results obtained from the analysis of the fast component of the stopped-flow kinetics should give the best value of the equilibrium constant between cytochrome f and plastocyanin. Fig.…”

Section: Resultsmentioning

confidence: 97%

Spectroscopic studies on electron transfer between plastocyanin and cytochrome b6f complex

Sujak¹,

Drepper²,

Haehnel³

2004

Journal of Photochemistry and Photobiology B: Biology

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Section: Resultsmentioning

confidence: 97%

Spectroscopic studies on electron transfer between plastocyanin and cytochrome b6f complex

Sujak¹,

Drepper²,

Haehnel³

2004

Journal of Photochemistry and Photobiology B: Biology

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“…One possibility is that Fd reduction accelerates its dissociation from PSI, in favor of an increased turnover, limited anyway to 800 -850 electrons/s. This rate is about five times larger than the reduction of cytochrome f by the Rieske protein, which is thought to be the rate-limiting step of oxygenic photosynthesis during linear electron transfer (64).…”

Section: Discussionmentioning

confidence: 99%

Ferredoxin-NADP+ Reductase

Cassan

Lagoutte

Sétif

2005

Journal of Biological Chemistry

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The electron transfer cascade from photosystem I to NADP ؉ was studied at physiological pH by flash-absorption spectroscopy in a Synechocystis PCC6803 reconstituted system comprised of purified photosystem I, ferredoxin, and ferredoxin-NADP ؉ reductase. Experiments were conducted with a 34-kDa ferredoxin-NADP ؉ reductase homologous to the chloroplast enzyme and a 38-kDa N-terminal extended form. Small differences in kinetic and catalytic properties were found for these two forms, although the largest one has a 3-fold decreased affinity for ferredoxin. The dissociation rate of reduced ferredoxin from photosystem I (800 s ؊1 ) and the redox potential of the first reduction of ferredoxin-NADP ؉ reductase (؊380 mV) were determined. In the absence of NADP ؉ , differential absorption spectra support the existence of a high affinity complex between oxidized ferredoxin and semireduced ferredoxin-NADP ؉ reductase. An effective rate of 140 -170 s ؊1 was also measured for the second reduction of ferredoxin-NADP ؉ reductase, this process having a rate constant similar to that of the first reduction. In the presence of NADP ؉ , the second-order rate constant for the first reduction of ferredoxin-NADP ؉ reductase was 20% slower than in its absence, in line with the existence of ternary complexes (ferredoxin-NADP ؉ reductase)-NADP ؉ -ferredoxin. A single catalytic turnover was monitored, with 50% NADP ؉ being reduced in 8 -10 ms using 1.6 M photosystem I. In conditions of multiple turnover, we determined initial rates of 360 -410 electrons per s and per ferredoxin-NADP ؉ reductase for the reoxidation of 3.5 M photoreduced ferredoxin. Identical rates were found with photosystem I lacking the PsaE subunit and wild type photosystem I. This suggests that, in contrast with previous proposals, the PsaE subunit is not involved in NADP ؉ photoreduction.

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“…In addition, some of the reactions involved in electron transfer within the cytochrome b 6 f complex have been dissected using flash kinetic spectroscopy. Soriano et al (2002) determined that reduction of cytochrome f by the Rieske FeS protein proceeds at 150 to 250 s 21 , with tethered movement of the protein from its quinol-proximal site to a region close to the cytochrome f heme representing the slowest process that limits the reaction. By comparison, other processes of the PETC take place much faster, with rate constants of approximately 800 s 21 for Fd reduction by PSI (Cassan et al, 2005), and 2,400 to 3,000 s 21 for electron transfer from cytochrome f to plastocyanin (Soriano et al, 2002).…”

Section: Photosynthesis In Fnr-mentioning

confidence: 99%

Transgenic Tobacco Plants Overexpressing Chloroplastic Ferredoxin-NADP(H) Reductase Display Normal Rates of Photosynthesis and Increased Tolerance to Oxidative Stress

et al. 2006

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(M.P., H.T., M.-R.H.)Ferredoxin-NADP(H) reductase (FNR) catalyzes the last step of photosynthetic electron transport in chloroplasts, driving electrons from reduced ferredoxin to NADP 1 . This reaction is rate limiting for photosynthesis under a wide range of illumination conditions, as revealed by analysis of plants transformed with an antisense version of the FNR gene. To investigate whether accumulation of this flavoprotein over wild-type levels could improve photosynthetic efficiency and growth, we generated transgenic tobacco (Nicotiana tabacum) plants expressing a pea (Pisum sativum) FNR targeted to chloroplasts. The alien product distributed between the thylakoid membranes and the chloroplast stroma. Transformants grown at 150 or 700 mmol quanta m 22 s 21 displayed wild-type phenotypes regardless of FNR content. Thylakoids isolated from plants with a 5-fold FNR increase over the wild type displayed only moderate stimulation (approximately 20%) in the rates of electron transport from water to NADP 1 . In contrast, when donors of photosystem I were used to drive NADP 1 photoreduction, the activity was 3-to 4-fold higher than the wild-type controls. Plants expressing various levels of FNR (from 1-to 3.6-fold over the wild type) failed to show significant differences in CO 2 assimilation rates when assayed over a range of light intensities and CO 2 concentrations. Transgenic lines exhibited enhanced tolerance to photooxidative damage and redox-cycling herbicides that propagate reactive oxygen species. The results suggest that photosynthetic electron transport has several rate-limiting steps, with FNR catalyzing just one of them.

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Electron Transfer from the Rieske Iron-Sulfur Protein (ISP) to Cytochrome f in Vitro

Cited by 25 publications

References 50 publications

Spectroscopic studies on electron transfer between plastocyanin and cytochrome b6f complex

Spectroscopic studies on electron transfer between plastocyanin and cytochrome b6f complex

Ferredoxin-NADP+ Reductase

Transgenic Tobacco Plants Overexpressing Chloroplastic Ferredoxin-NADP(H) Reductase Display Normal Rates of Photosynthesis and Increased Tolerance to Oxidative Stress

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