Temperature dependence of the reduction of p-700(+) by tightly bound plastocyanin in vivo

S. Santabarbara, K.E. Redding, F. Rappaport

Research output: Contribution to journalArticle

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Abstract

The kinetics of reduction of P(700)(+), the stably oxidized electron donor of Photosystem I, by plastocyanin (PC) has been investigated by pump-probe optical spectroscopy in living cells of the green alga Chlamydomonas reinhardtii, between 277 and 318 K. The reduction of P(700)(+) in vivo is described by two kinetic components with lifetimes of 6 +/- 0.5 and 56 +/- 1 micros at room temperature. The rapid reduction phase, which is attributed to reduction of P(700)(+) by prebound PC, is thermally activated with an apparent activation barrier of 105-115 meV. The analysis of the in vivo reaction is consistent with (i) reduced PC and PS I forming a relatively tight binary complex that does not undergo kinetically limiting conformational reconfiguration and (ii) the activation barrier being determined principally by enthalpic contributions to the free energy change. Under the approximation that entropic contributions to the free energy change associated with this electron transfer reaction are negligible, a lower boundary value of the reorganization energy is estimated to be 0.54-0.63 eV, which is on the lower range of the distribution for intraprotein electron transfer reactions. This low activation barrier is discussed in terms of the optimization of primary donor reduction.
LanguageEnglish
Pages10457-10466
Number of pages9
JournalBMC Biochemistry
Volume48
Issue number43
DOIs
Publication statusPublished - 3 Nov 2009

Fingerprint

Plastocyanin
Electrons
Temperature
Chemical activation
Photosystem I Protein Complex
Chlamydomonas reinhardtii
Chlorophyta
Free energy
Spectrum Analysis
Kinetics
Algae
Cells
chlorophyll P 700
Pumps

Keywords

  • photosynthetic reaction-center
  • electron-transfer reactions
  • photosystem-i
  • rhodobacter-sphaeroides
  • cytochrome c(2)
  • chlamydomonas-reinhardtii
  • spinach plastocyanin
  • flash-photolysis
  • biological molecules
  • reaction centers

Cite this

Santabarbara, S. ; Redding, K.E. ; Rappaport, F. / Temperature dependence of the reduction of p-700(+) by tightly bound plastocyanin in vivo. In: BMC Biochemistry. 2009 ; Vol. 48, No. 43. pp. 10457-10466.
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abstract = "The kinetics of reduction of P(700)(+), the stably oxidized electron donor of Photosystem I, by plastocyanin (PC) has been investigated by pump-probe optical spectroscopy in living cells of the green alga Chlamydomonas reinhardtii, between 277 and 318 K. The reduction of P(700)(+) in vivo is described by two kinetic components with lifetimes of 6 +/- 0.5 and 56 +/- 1 micros at room temperature. The rapid reduction phase, which is attributed to reduction of P(700)(+) by prebound PC, is thermally activated with an apparent activation barrier of 105-115 meV. The analysis of the in vivo reaction is consistent with (i) reduced PC and PS I forming a relatively tight binary complex that does not undergo kinetically limiting conformational reconfiguration and (ii) the activation barrier being determined principally by enthalpic contributions to the free energy change. Under the approximation that entropic contributions to the free energy change associated with this electron transfer reaction are negligible, a lower boundary value of the reorganization energy is estimated to be 0.54-0.63 eV, which is on the lower range of the distribution for intraprotein electron transfer reactions. This low activation barrier is discussed in terms of the optimization of primary donor reduction.",
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Temperature dependence of the reduction of p-700(+) by tightly bound plastocyanin in vivo. / Santabarbara, S.; Redding, K.E.; Rappaport, F.

In: BMC Biochemistry, Vol. 48, No. 43, 03.11.2009, p. 10457-10466.

Research output: Contribution to journalArticle

TY - JOUR

T1 - Temperature dependence of the reduction of p-700(+) by tightly bound plastocyanin in vivo

AU - Santabarbara, S.

AU - Redding, K.E.

AU - Rappaport, F.

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AB - The kinetics of reduction of P(700)(+), the stably oxidized electron donor of Photosystem I, by plastocyanin (PC) has been investigated by pump-probe optical spectroscopy in living cells of the green alga Chlamydomonas reinhardtii, between 277 and 318 K. The reduction of P(700)(+) in vivo is described by two kinetic components with lifetimes of 6 +/- 0.5 and 56 +/- 1 micros at room temperature. The rapid reduction phase, which is attributed to reduction of P(700)(+) by prebound PC, is thermally activated with an apparent activation barrier of 105-115 meV. The analysis of the in vivo reaction is consistent with (i) reduced PC and PS I forming a relatively tight binary complex that does not undergo kinetically limiting conformational reconfiguration and (ii) the activation barrier being determined principally by enthalpic contributions to the free energy change. Under the approximation that entropic contributions to the free energy change associated with this electron transfer reaction are negligible, a lower boundary value of the reorganization energy is estimated to be 0.54-0.63 eV, which is on the lower range of the distribution for intraprotein electron transfer reactions. This low activation barrier is discussed in terms of the optimization of primary donor reduction.

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KW - rhodobacter-sphaeroides

KW - cytochrome c(2)

KW - chlamydomonas-reinhardtii

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KW - flash-photolysis

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