The role of plastoquinone in the in vivo photosynthetic cyclic electron transport pathway in algae

Biggins, John

doi:10.1016/0014-5793(74)80080-3

Cited by 13 publications

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“…Because the cycle may use soluble electron transport components, such as Fd or NADPH, this largely precludes studies of refined PSI particles. In a series of seminal papers, Biggins and co-workers inferred the existence of cyclic electron flow by measuring the kinetics of Cyt f tumover (Biggins, 1974a(Biggins, , 1974b and P700+ reduction Biggins, 1976, 1977) in PSII mutants and in the presence of various PSI and PSII inhibitors. The slow kinetics of P700+ reduction under conditions appropriate for cyclic flow led them to conclude that cyclic electron transport does not contribute appreciably to photosynthesis in oxygenevolving autotrophs.…”

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PsaE Is Required for in Vivo Cyclic Electron Flow around Photosystem I in the Cyanobacterium Synechococcus sp. PCC 7002

et al. 1993

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Electron transfer rates to P700' have been determined in wildtype and three interposon mutants (psaE-, ndhf-, and psaE-ndhf-) of Synechococcus sp. PCC 7002. All three mutants grew significantly more slowly than wild type at low light intensities, and each failed to grow photoheterotrophically in the presence of 3-(3,4-dichloropheny1)-1,l-dimethylurea (DCMU) and a metabolizable carbon source. l h e kinetics of P700+ reduction were similar in the wild-type and mutant whole cells in the absence of DCMU. In the presence of DCMU, the P700+ reduction rate in the psaE mutant was significantly slower than in the wild type. In the presence of DCMU and potassium cyanide, added to inhibit the outflow of electrons through cytochrome oxidase, P700+ reduction rates increased for both the psaE-and ndhF-strains. The reduction rates for these two mutants were nonetheless slower than that observed for the wild-type strain. l h e further addition of methyl viologen caused the rate of P700+ reduction in the wild type to become as slow as that for the psaE mutant in the absence of methyl viologen. Civen the ability of methyl viologen to intercept electrons from the acceptor side of photosystem I, this response reveals a lesion in cyclic electron flow in the psaE mutant. In the presence of DCMU, the rate of P700' reduction in the psaE ndhf double mutant was very slow and nearly identical with that for the wild-type strain in the presence of 2,4-dibromo-3-methyl-6-isopropyl-p-benzoquinone, a condition under which physiological electron donation to P700+ should be completely inhibited. These results suggest that NdhF-and PsaE-dependent electron donation to P700+ occurs only via plastoquinone and/or cytochrome b6/f and indicate that there are three major electron sources for P700+ reduction in this cyanobacterium. We conclude that, although PsaE is not required for linear electron flow to NADP+, it is an essential component in the cyclic electron transport pathway around photosystem 1.

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PsaE Is Required for in Vivo Cyclic Electron Flow around Photosystem I in the Cyanobacterium Synechococcus sp. PCC 7002

et al. 1993

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“…A previous report from this laboratory described a kinetic analysis of the photo-induced turnover of cytochrome / in Porphyridium cruentum during cyclic and noncyclic electron transport (Biggins, 1973). It was concluded from direct spectrophotometric measurements on intact cells that cyclic electron transport does not contribute to the photoassimilation of carbon dioxide.…”

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Role of cyclic electron transport in photosynthesis as measured by the photoinduced turnover of P700 in vivo

Maxwell¹,

Biggins²

1976

Biochemistry

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113

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The light-induced turnover of P700 was measured spectrophotometrically in a wide variety of algae and some photosynthetic mutants. Analysis of the postillumination recovery of P700+ revealed that the apparent first-order rate constant for reduction via the cyclic pathway was much lower that that via the noncyclic pathway. After activation of photosystems 1 and 2 the half-time for reduction of P700+ was 5-20 ms, whereas after activation of primarily photosystem 1 a longer half-time of ca. 150 ms was observed. The extent of the photooxidation of P700 was the same in both regimes of illumination. The longer half-time was also noted after inhibition of photosystem 2 by 3-(3,4-dichlorophenyl)-1,1-dimethylurea or mild heat shock and in mutant algae known to lack a functional photosystem 2. No signal was observed in mutants lacking P700 itself but those strains lacking either plastocyanin or cytochrome f were capable of a very slow turnover (reduction t 1/2 greater than 500 ms at room temperature). This very slow turnover was not affected by carbonyl cyanide m-chlorophenylhydrazone or the plastoquinone antagonist, 2,5-dibromo-3-methyl-6-isopropyl-p-benzoquinone, indicating that the pathway for reduction of P700+ in these mutants is not energy linked and does not utilize the intersystem electron transport chain. The slow, 150 ms, reduction of P700+ due to cyclic flow was not observed when cells were engaged in photosynthesis at high-light intensities. The data are interpreted as evidence for the involvement of the total functional pool of P700 in both electron transport pathways, and we suggest that cyclic electron transport does not contribute to photosynthesis in oxygen-evolving autotrophs.

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“…Photooxidation of cytochrome hg, a specific component of cyclic electron flow [3,4], appears to involve a number of components common to both cyclic and non-cyclic electron transport [4-61. Experiments with isolated chloroplasts, photosystem-I fragments and algal mutants suggest an involvement of plastoquinone [4,9], cytochromef [8], plastocyanin [5,6] and P-700 [5], a special chlorophyll-a molecule in the reaction center of photosystem I [lo]. Electron carriers participating in cytochrome 6.5 reduction, on the other hand, have so far not been investigated.…”

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On the Role of Ferredoxin and Ferredoxin‐NADP⁺Reductase in Cyclic Electron Transport of Spinach Chloroplasts

Böhme

1977

European Journal of Biochemistry

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Antibodies prepared against purified spinach ferredoxin and ferredoxin‐NADP+ reductase were used as specific inhibitors of electron‐transfer reactions dependent on either ferredoxin or ferredoxin‐NADP+ reductase. The possible role of both electron carriers in cyclic electron transport was checked using cytochrome b6 photoreactions as indicator. It could be demonstrated that the ferredoxin antibody inhibits cytochrome b6 photoreduction. Ferredoxin‐NADP+ reductase, however, appears not to be involved in this pathway: reductase antibody in concentrations sufficient to completely inhibit electron transport to NADP+ had no effect on cytochrome b6 photoreduction. Quantitative treatment of the immunoassay data showed that osmotically shocked chloroplasts contain both bound ferredoxin and ferredoxin‐NADP+ reductase in concentrations approximately equal to that of cytochrome b6.

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The role of plastoquinone in the in vivo photosynthetic cyclic electron transport pathway in algae

Cited by 13 publications

References 14 publications

PsaE Is Required for in Vivo Cyclic Electron Flow around Photosystem I in the Cyanobacterium Synechococcus sp. PCC 7002

PsaE Is Required for in Vivo Cyclic Electron Flow around Photosystem I in the Cyanobacterium Synechococcus sp. PCC 7002

Role of cyclic electron transport in photosynthesis as measured by the photoinduced turnover of P700 in vivo

On the Role of Ferredoxin and Ferredoxin‐NADP⁺Reductase in Cyclic Electron Transport of Spinach Chloroplasts

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The role of plastoquinone in the in vivo photosynthetic cyclic electron transport pathway in algae

Cited by 13 publications

References 14 publications

PsaE Is Required for in Vivo Cyclic Electron Flow around Photosystem I in the Cyanobacterium Synechococcus sp. PCC 7002

PsaE Is Required for in Vivo Cyclic Electron Flow around Photosystem I in the Cyanobacterium Synechococcus sp. PCC 7002

Role of cyclic electron transport in photosynthesis as measured by the photoinduced turnover of P700 in vivo

On the Role of Ferredoxin and Ferredoxin‐NADP+Reductase in Cyclic Electron Transport of Spinach Chloroplasts

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On the Role of Ferredoxin and Ferredoxin‐NADP⁺Reductase in Cyclic Electron Transport of Spinach Chloroplasts