Critical evaluation of electron transfer kinetics in P700–FA/FB, P700–FX, and P700–A1 Photosystem I core complexes in liquid and in trehalose glass

Vasily Kurashov, Michael Gorka, Georgy E. Milanovsky, T. Wade Johnson, Dmitry A. Cherepanov, Alexey Yu Semenov, John H. Golbeck

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Abstract

This work aims to fully elucidate the effects of a trehalose glassy matrix on electron transfer reactions in cyanobacterial Photosystem I (PS I). Forward and backward electron transfer rates from A1A and A1B to FX, and charge recombination rates from A0 , A1B , A1A , FX , and [FA/FB] to P700 + were measured in P700–FA/FB complexes, P700–FX cores, and P700–A1 cores, both in liquid and in a trehalose glassy matrix at 11% humidity. By comparing CONTIN-resolved kinetic events over 6 orders of time in increasingly simplified versions of PS I at 480 nm, a wavelength that reports primarily A1A /A1B oxidation, and over 9 orders of time at 830 nm, a wavelength that reports P700 + reduction and A0 oxidation, assignments could be made for nearly all of the resolved kinetic phases. Trehalose-embedded PS I samples demonstrated partially arrested forward electron transfer. The fractions of complexes in which electron transfer did not proceed beyond A0, A1 and FX were 53%, 16% and 22%, respectively, with only 10% of electrons reaching the terminal FA/FB clusters. The ~10 μs and ~150 μs components in both liquid and trehalose-embedded PS I were assigned to recombination between A1B and P700 + and between A1A and P700 +, respectively. The kinetics and amplitudes of these resolved kinetic phases in liquid and trehalose-embedded PS I samples could be well-fitted by a kinetic model that allowed us to calculate the asymmetrical contribution of the A1A and A1B quinones to the electrochromic signal at 480 nm. Possible reasons for these effects are discussed.

Original languageEnglish (US)
Pages (from-to)1288-1301
Number of pages14
JournalBiochimica et Biophysica Acta - Bioenergetics
Volume1859
Issue number12
DOIs
StatePublished - Dec 2018

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All Science Journal Classification (ASJC) codes

  • Biophysics
  • Biochemistry
  • Cell Biology

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