Alteration of the H-Bond to the A1A phylloquinone in photosystem I

Influence on the kinetics and energetics of electron transfer

Nithya Srinivasan, Stefano Santabarbara, Fabrice Rappaport, Donatella Carbonera, Kevin Redding, Art Van Der Est, John H. Golbeck

Research output: Contribution to journalArticle

17 Citations (Scopus)

Abstract

In Photosystem I, the backbone nitrogen of Leu722PsaA forms a hydro-gen bond with the C4 carbonyl oxygen of phylloquinone in the A1A site. A previous low-temperature EPR study indicated that substitution of Leu722PsaA with a bulky Trp residue results in a weakened H-bond. Here, we employ room temperature, time-resolved optical spectroscopy and variable temperature, transient EPR spectroscopy to probe the effect of the altered H-bond on the energetics and kinetics of electron transfer. Relative to the wild type, we find that the rate of electron transfer from A1A- to FX in the L722WPsaA variant is faster by a factor of 3. This change is attributed to a lowered midpoint potential of A1A/A1A-, resulting in a larger Gibbs free energy change between A1A/A1A - and FX/FX-. An activation energy of 180 ± 10 meV is determined for the A1A--to- FX forward electron transfer step in the L722WPsaA variant compared with 220 ± 10 meV in the wild type. The Arrhenius plot shows a break at ∼200 K, below which the rate becomes nearly independent of temperature. This behavior is described using a quantum mechanical treatment that takes the zero-point energy into account as well as an alternative model that invokes a dynamical transition in the protein at ∼200 K.

Original languageEnglish (US)
Pages (from-to)1751-1759
Number of pages9
JournalJournal of Physical Chemistry B
Volume115
Issue number8
DOIs
StatePublished - Mar 3 2011

Fingerprint

phylloquinone
Vitamin K 1
Photosystem I Protein Complex
electron transfer
Kinetics
Electrons
kinetics
Paramagnetic resonance
zero point energy
Gibbs free energy
Arrhenius plots
Temperature
spectroscopy
plots
substitutes
activation energy
proteins
nitrogen
Substitution reactions
Nitrogen

All Science Journal Classification (ASJC) codes

  • Physical and Theoretical Chemistry
  • Surfaces, Coatings and Films
  • Materials Chemistry

Cite this

Srinivasan, Nithya ; Santabarbara, Stefano ; Rappaport, Fabrice ; Carbonera, Donatella ; Redding, Kevin ; Van Der Est, Art ; Golbeck, John H. / Alteration of the H-Bond to the A1A phylloquinone in photosystem I : Influence on the kinetics and energetics of electron transfer. In: Journal of Physical Chemistry B. 2011 ; Vol. 115, No. 8. pp. 1751-1759.
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Alteration of the H-Bond to the A1A phylloquinone in photosystem I : Influence on the kinetics and energetics of electron transfer. / Srinivasan, Nithya; Santabarbara, Stefano; Rappaport, Fabrice; Carbonera, Donatella; Redding, Kevin; Van Der Est, Art; Golbeck, John H.

In: Journal of Physical Chemistry B, Vol. 115, No. 8, 03.03.2011, p. 1751-1759.

Research output: Contribution to journalArticle

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T1 - Alteration of the H-Bond to the A1A phylloquinone in photosystem I

T2 - Influence on the kinetics and energetics of electron transfer

AU - Srinivasan, Nithya

AU - Santabarbara, Stefano

AU - Rappaport, Fabrice

AU - Carbonera, Donatella

AU - Redding, Kevin

AU - Van Der Est, Art

AU - Golbeck, John H.

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