Turnover of ubiquinone-0 at the acceptor side of photosynthetic reaction center

László Gerencsér, P. Maróti

Research output: Contribution to journalArticle

3 Citations (Scopus)

Abstract

The steady-state operation of photosynthetic reaction center from Rhodobacter sphaeroides was investigated by measuring the rate of cytochrome photo-oxidation under intensive continuous illumination (808 nm, 5 W cm -2). The native quinone UQ10 in QB binding site of the reaction center was substituted by tailless UQ0 and the binding parameters and the turnover rate of the UQ0 was studied to test the recently discovered light-intensity dependent acceptor side effect (Gerencsér and Maróti 2006). The binding parameters of UQ 0 (k on = 2.1 × 105 M-1 s -1 and k off = 100 s-1) were characteristic to the RC exposed to high light-intensity. The dissociation constant (K D = 480 μM) determined under high light intensity is 2-3 times larger than that determined from flash-experiments. The light-intensity dependent acceleration of cytochrome turnover measured on reaction center of inhibited proton binding was independent of the type of the quinone and was sensitive only to the size ("pressure") of the quinone pool. The dissociation constants of different types of semiquinones show similarly high (several orders of magnitude) increase in the modified conformation of the QB binding pocket due to high intensity of illumination. This result indicates the exclusive role of the quinone headgroup in the binding of semiquinone to different conformations of the protein.

Original languageEnglish
Pages (from-to)1195-1205
Number of pages11
JournalEuropean Biophysics Journal
Volume37
Issue number7
DOIs
Publication statusPublished - Sep 2008

Fingerprint

Photosynthetic Reaction Center Complex Proteins
Light
Cytochromes
Lighting
Rhodobacter sphaeroides
Protein Conformation
Protons
Binding Sites
Pressure
ubiquinone-O
benzoquinone

Keywords

  • Bacterial photosynthesis
  • Cytochrome turnover
  • Quinone binding
  • Reaction center protein
  • Redox potentiometry

ASJC Scopus subject areas

  • Biophysics

Cite this

Turnover of ubiquinone-0 at the acceptor side of photosynthetic reaction center. / Gerencsér, László; Maróti, P.

In: European Biophysics Journal, Vol. 37, No. 7, 09.2008, p. 1195-1205.

Research output: Contribution to journalArticle

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