Modeling of the P700 + charge recombination kinetics with phylloquinone and plastoquinone-9 in the A 1 site of photosystem I

Vladimir P. Shinkarev, Boris Zybailov, Ilya R. Vassiliev, John H. Golbeck

Research output: Contribution to journalArticle

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Abstract

Light activation of photosystem I (PS I) induces electron transfer from the excited primary electron donor P700 (a special pair of chlorophyll a/a′ molecules) to three iron-sulfur clusters, F X , F A , and F B via acceptors A O (a monomeric chlorophyll a) and A 1 (phylloquinone). PS I complexes isolated from menA and menB mutants contain plastoquinone-9 rather than phylloquinone in the A 1 site and show altered rates of forward electron transfer from A 1 - to [F A /F B ] and altered rates of back electron transfer from [F A /F B ] - to P700 + (Semenov, A. Y., et al., J. Biol. Chem. 275:23429-23438, 2000). To identify the modified electron transfer steps, we studied the kinetics of flash-induced P700 + reduction in PS I that contains either an intact set or a subset of iron-sulfur clusters F X , F A , and F B and with the A 1 binding site occupied by phylloquinone or plastoquinone-9. A modeling of the forward and backward electron transfer kinetics in P700-F A /F B complexes, P700-F X cores, and P700-A 1 cores shows that the replacement of phylloquinone by plastoquinone-9 induces a decrease in the free energy gap between A 1 and F A /F B from ∼-205 mV in wild-type PS I to ∼-70 mV in menA PS I. The +135 mV increase in the midpoint potential of A 1 explains the acceleration in the rate of P700 + dark reduction in menA PS I, and the resulting uphill electron transfer from A 1 to F X in menA PS I explains the absence of a contribution from F X - to the reduction of P700 + . This fully quantitative description of PS I relates electron transfer rates, equilibrium constants, and redox potentials, and can be used to predict changes in these parameters upon substitution of electron transfer cofactors.

Original languageEnglish (US)
Pages (from-to)2885-2897
Number of pages13
JournalBiophysical journal
Volume83
Issue number6
DOIs
StatePublished - Dec 1 2002

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Plastoquinone
Vitamin K 1
Photosystem I Protein Complex
Genetic Recombination
Electrons
Sulfur
Iron
Oxidation-Reduction
Binding Sites

All Science Journal Classification (ASJC) codes

  • Biophysics

Cite this

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title = "Modeling of the P700 + charge recombination kinetics with phylloquinone and plastoquinone-9 in the A 1 site of photosystem I",
abstract = "Light activation of photosystem I (PS I) induces electron transfer from the excited primary electron donor P700 (a special pair of chlorophyll a/a′ molecules) to three iron-sulfur clusters, F X , F A , and F B via acceptors A O (a monomeric chlorophyll a) and A 1 (phylloquinone). PS I complexes isolated from menA and menB mutants contain plastoquinone-9 rather than phylloquinone in the A 1 site and show altered rates of forward electron transfer from A 1 - to [F A /F B ] and altered rates of back electron transfer from [F A /F B ] - to P700 + (Semenov, A. Y., et al., J. Biol. Chem. 275:23429-23438, 2000). To identify the modified electron transfer steps, we studied the kinetics of flash-induced P700 + reduction in PS I that contains either an intact set or a subset of iron-sulfur clusters F X , F A , and F B and with the A 1 binding site occupied by phylloquinone or plastoquinone-9. A modeling of the forward and backward electron transfer kinetics in P700-F A /F B complexes, P700-F X cores, and P700-A 1 cores shows that the replacement of phylloquinone by plastoquinone-9 induces a decrease in the free energy gap between A 1 and F A /F B from ∼-205 mV in wild-type PS I to ∼-70 mV in menA PS I. The +135 mV increase in the midpoint potential of A 1 explains the acceleration in the rate of P700 + dark reduction in menA PS I, and the resulting uphill electron transfer from A 1 to F X in menA PS I explains the absence of a contribution from F X - to the reduction of P700 + . This fully quantitative description of PS I relates electron transfer rates, equilibrium constants, and redox potentials, and can be used to predict changes in these parameters upon substitution of electron transfer cofactors.",
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Modeling of the P700 + charge recombination kinetics with phylloquinone and plastoquinone-9 in the A 1 site of photosystem I . / Shinkarev, Vladimir P.; Zybailov, Boris; Vassiliev, Ilya R.; Golbeck, John H.

In: Biophysical journal, Vol. 83, No. 6, 01.12.2002, p. 2885-2897.

Research output: Contribution to journalArticle

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T1 - Modeling of the P700 + charge recombination kinetics with phylloquinone and plastoquinone-9 in the A 1 site of photosystem I

AU - Shinkarev, Vladimir P.

AU - Zybailov, Boris

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N2 - Light activation of photosystem I (PS I) induces electron transfer from the excited primary electron donor P700 (a special pair of chlorophyll a/a′ molecules) to three iron-sulfur clusters, F X , F A , and F B via acceptors A O (a monomeric chlorophyll a) and A 1 (phylloquinone). PS I complexes isolated from menA and menB mutants contain plastoquinone-9 rather than phylloquinone in the A 1 site and show altered rates of forward electron transfer from A 1 - to [F A /F B ] and altered rates of back electron transfer from [F A /F B ] - to P700 + (Semenov, A. Y., et al., J. Biol. Chem. 275:23429-23438, 2000). To identify the modified electron transfer steps, we studied the kinetics of flash-induced P700 + reduction in PS I that contains either an intact set or a subset of iron-sulfur clusters F X , F A , and F B and with the A 1 binding site occupied by phylloquinone or plastoquinone-9. A modeling of the forward and backward electron transfer kinetics in P700-F A /F B complexes, P700-F X cores, and P700-A 1 cores shows that the replacement of phylloquinone by plastoquinone-9 induces a decrease in the free energy gap between A 1 and F A /F B from ∼-205 mV in wild-type PS I to ∼-70 mV in menA PS I. The +135 mV increase in the midpoint potential of A 1 explains the acceleration in the rate of P700 + dark reduction in menA PS I, and the resulting uphill electron transfer from A 1 to F X in menA PS I explains the absence of a contribution from F X - to the reduction of P700 + . This fully quantitative description of PS I relates electron transfer rates, equilibrium constants, and redox potentials, and can be used to predict changes in these parameters upon substitution of electron transfer cofactors.

AB - Light activation of photosystem I (PS I) induces electron transfer from the excited primary electron donor P700 (a special pair of chlorophyll a/a′ molecules) to three iron-sulfur clusters, F X , F A , and F B via acceptors A O (a monomeric chlorophyll a) and A 1 (phylloquinone). PS I complexes isolated from menA and menB mutants contain plastoquinone-9 rather than phylloquinone in the A 1 site and show altered rates of forward electron transfer from A 1 - to [F A /F B ] and altered rates of back electron transfer from [F A /F B ] - to P700 + (Semenov, A. Y., et al., J. Biol. Chem. 275:23429-23438, 2000). To identify the modified electron transfer steps, we studied the kinetics of flash-induced P700 + reduction in PS I that contains either an intact set or a subset of iron-sulfur clusters F X , F A , and F B and with the A 1 binding site occupied by phylloquinone or plastoquinone-9. A modeling of the forward and backward electron transfer kinetics in P700-F A /F B complexes, P700-F X cores, and P700-A 1 cores shows that the replacement of phylloquinone by plastoquinone-9 induces a decrease in the free energy gap between A 1 and F A /F B from ∼-205 mV in wild-type PS I to ∼-70 mV in menA PS I. The +135 mV increase in the midpoint potential of A 1 explains the acceleration in the rate of P700 + dark reduction in menA PS I, and the resulting uphill electron transfer from A 1 to F X in menA PS I explains the absence of a contribution from F X - to the reduction of P700 + . This fully quantitative description of PS I relates electron transfer rates, equilibrium constants, and redox potentials, and can be used to predict changes in these parameters upon substitution of electron transfer cofactors.

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