Light-Induced Conformational Changes in Photosynthetic Reaction Centers

Redox-Regulated Proton Pathway near the Dimer

Sasmit S. Deshmukh, Joann C. Williams, James P. Allen, László Kálmán

Research output: Contribution to journalArticle

11 Citations (Scopus)

Abstract

The influence of the hydrogen bonds on the light-induced structural changes were studied in the wild type and 11 mutants with different hydrogen bonding patterns of the primary electron donor of reaction centers from Rhodobacter sphaeroides. Previously, using the same set of mutants at pH 8, a marked light-induced change of the local dielectric constant in the vicinity of the dimer was reported in wild type and in mutants retaining Leu L131 that correlated with the recovery kinetics of the charge-separated state [Deshmukhet al. (2011) Biochemistry, 50, 340 -348]. In this work after prolonged illumination the recovery of the oxidized dimer was found to be multiphasic in all mutants. The fraction of the slowest phase, assigned to a recovery from a conformationally altered state, was strongly pH dependent and found to be extremely long at room temperature, at pH 6, with rate constants of 10 -3 s-1. In wild type and in mutants with Leu at L131 the very long recovery kinetics was coupled to a large proton release at pH 6 and a decrease of up to 79 mV of the oxidation potential of the dimer. In contrast, in the mutants carrying the Leu to His mutation at the L131 position, only a negligible fraction of the dimer exhibited lowered potential, the large proton release was not observed, the oxidized dimer recovered 1 or 2 orders of magnitude faster depending on the pH, and the very long-lived state was not or barely detectable. These results are modeled as arising from the loss of a proton pathway from the bacteriochlorophyll dimer to the solvent when His is present at the L131 position.

Original languageEnglish
Pages (from-to)3321-3331
Number of pages11
JournalBiochemistry
Volume50
Issue number16
DOIs
Publication statusPublished - Apr 26 2011

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Photosynthetic Reaction Center Complex Proteins
Dimers
Oxidation-Reduction
Protons
Light
Recovery
Hydrogen bonds
Bacteriochlorophylls
Rhodobacter sphaeroides
Hydrogen Bonding
Biochemistry
Kinetics
Lighting
Hydrogen
Electrons
Rate constants
Permittivity
Mutation
Temperature
Oxidation

ASJC Scopus subject areas

  • Biochemistry

Cite this

Light-Induced Conformational Changes in Photosynthetic Reaction Centers : Redox-Regulated Proton Pathway near the Dimer. / Deshmukh, Sasmit S.; Williams, Joann C.; Allen, James P.; Kálmán, László.

In: Biochemistry, Vol. 50, No. 16, 26.04.2011, p. 3321-3331.

Research output: Contribution to journalArticle

Deshmukh, Sasmit S. ; Williams, Joann C. ; Allen, James P. ; Kálmán, László. / Light-Induced Conformational Changes in Photosynthetic Reaction Centers : Redox-Regulated Proton Pathway near the Dimer. In: Biochemistry. 2011 ; Vol. 50, No. 16. pp. 3321-3331.
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