Kinetic identification of Component X as P430: A primary electron acceptor of Photosystem I

Hiyama, Tetsuo; Fork, David C.

doi:10.1016/0003-9861(80)90306-9

Cited by 25 publications

(5 citation statements)

References 17 publications

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“…On the other hand, support for F x not being the reductant for F A and F B came from a study by Hiyama and Fork [49]. In this work F x was kinetically correlated with an absorbance change at 4 3 0 n m and the addition of soluble ferredoxin was seen to speed up the oxidation of trapped F x (as monitored by the absorbance change).…”

Section: Is F X the Acceptor That Precedes Fb/f A In Forward Electronmentioning

confidence: 87%

“…illumination of a non-frozen sample in the presence of a reductant [42,49,57,66,106]. Difference spectra of 'A~' minus 'A2' obtained in this manner also suggested that A2 was equivalent to F x and that this component could be an iron sulphur center.…”

Section: Oomentioning

confidence: 93%

“…However this assignment is questionable since several components probably give rise to absorption changes at this wavelength [see e.g., 49].…”

Section: Fa An Early Electron Acceptormentioning

confidence: 99%

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Primary photochemistry in photosystem-I

1985

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In this review, the main research developments that have led to the current simplified picture of photosystem I are presented. This is followed by a discussion of some conflicting reports and unresolved questions in the literature. The following points are made: (1) the evidence is contradictory on whether P700, the primary donor, is a monomer or dimer of chlorophyll although at this time the balacnce of the evidence points towards a monomeric structure for P700 when in the triplet state; (2) there is little evidence that the iron sulfur centers FA and FB act in series as tertiary acceptors and it is as likely that they act in parallel under physiological conditions; (3) a role for FX, probably another iron sulfur centrer, as an obligatory electron carrier in forward electron transfer has not been proven. Some evidence indicates that its reduction could represent a pathway different to that involving FA and FB; (4) the decay of the acceptor 'A2 (-)' as defined by optical spectroscopy corresponds with 700(+) % MathType!MTEF!2!1!+-% feaafeart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9% vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x% fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaamOramaaBa% aaleaadaqdaaqaaiaadIfaaaaabeaaaaa!37D1!\[F_{\overline X } \] recombination under some circumstances but under other conditions it probably corresponds with P700(+) A1 (-) recombination; (5) P700(+) A1 (-) recombination as originally observed by optical spectroscopy is probably due to the decay of the P700 triplet state; (6) the acceptor A1 (-) as defined by EPR may be a special semiquinone molecule; (7) A0 is probably a chlorophyll a molecule which acts as the primary acceptor. Recombination of P700(+) A0 (-) gives rise to the P700 triplet state.A working model for electron transfer in photosystem I is presented, its general features are discussed and comparisons with other photosystems are made.

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Section: Is F X the Acceptor That Precedes Fb/f A In Forward Electronmentioning

confidence: 87%

Section: Oomentioning

confidence: 93%

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Primary photochemistry in photosystem-I

1985

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“…There is actually little direct evidence to support a role for F; as the direct donor of electrons to FA and FB and there are in fact some indications that F x may operate in parallel to the other two iron-sulfur centers (e.g., HIYAMA and FoRK 1980). There is actually little direct evidence to support a role for F; as the direct donor of electrons to FA and FB and there are in fact some indications that F x may operate in parallel to the other two iron-sulfur centers (e.g., HIYAMA and FoRK 1980).…”

Section: The Acceptor-side Components and Reactions Of Photosystem Imentioning

confidence: 99%

Energy Transduction in Oxygenic Photosynthesis: An Overview of Structure and Mechanism

Ort¹

1986

Photosynthesis III

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“…3. Some workers proposed F x as P430 (Hiyama and Fork 1980). With HgCIE-treated particles, it is also unclear whether the destruction of FB affects the rate of charge recombination between F x and P700 ÷ and whether the remnant of Fa, although invisible in EPR spectra, is still able to accept an electron from F x.…”

Section: Introductionmentioning

confidence: 99%

Effects of selective destruction of iron-sulfur center B on electron transfer and charge recombination in Photosystem I

1991

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Incubation of spinach thylakoids with HgCl2 selectively destroys Fe-S center B (FB). The function of electron acceptors in FB-less PS I particles was studied by following the decay kinetics of P700(+) at room temperature after multiple flash excitation in the absence of a terminal electron acceptor. In untreated particles, the decay kinetics of the signal after the first and the second flashes were very similar (t 1/2∼2.5 ms), and were principally determined by the concentration of the artificial electron donor added. The decay after the third flash was fast (t 1/2∼0.25 ms). In FB-less particles, although the decay after the first flash was slow, fast decay was observed already after the second flash. We conclude that in FB-less particles, electron transfer can proceed normally at room temperature from FX to FA and that the charge recombination between P700(+) and FX (-)/A1 (-) predominated after the second excitation. The rate of this recombination process is not significantly affected by the destruction of FB. Even in the presence of 60% glycerol, FB-less particles can transfer electrons to FA at room temperature as efficiently as untreated particles.

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Kinetic identification of Component X as P430: A primary electron acceptor of Photosystem I

Cited by 25 publications

References 17 publications

Primary photochemistry in photosystem-I

Primary photochemistry in photosystem-I

Energy Transduction in Oxygenic Photosynthesis: An Overview of Structure and Mechanism

Effects of selective destruction of iron-sulfur center B on electron transfer and charge recombination in Photosystem I

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