Mutational control of bioenergetics of bacterial reaction center probed by delayed fluorescence

Delphine Onidas, Gábor Sipka, Emese Asztalos, P. Maróti

Research output: Contribution to journalArticle

5 Citations (Scopus)

Abstract

The free energy gap between the metastable charge separated state P+QA - and the excited bacteriochlorophyll dimer P wasmeasured by delayed fluorescence of the dimer inmutant reaction center proteins of the photosynthetic bacterium Rhodobacter sphaeroides. The mutations were engineered both at the donor (L131L, M160L, M197F and M202H) and acceptor (M265I and M234E) sides.While the donor side mutations changed systematically the number of H-bonds to P, the acceptor side mutations modified the energetics of QA by altering the van-der-Waals and electronic interactions (M265IT) and H-bond network to the acidic cluster around QB (M234EH, M234EL, M234EA and M234ER). All mutants decreased the free energy gap of the wild type RC (∼890 meV), i.e. destabilized the P+QA - charge pair by 60-110 meV at pH 8.Multiplemodifications in the hydrogen bonding pattern to P resulted in systematic changes of the free energy gap. The destabilization showed no pH-dependence (M234 mutants) or slight increase (WT, donor-side mutants and M265IT above pH 8) with average slope of 10-15 meV/pH unit over the 6-10.5 pH range. In wild type and donor-side mutants, the free energy change of the charge separation consisted of mainly enthalpic term but the acceptor side mutants showed increased entropic (even above that of enthalpic) contributions. This could include softening the structure of the iron ligand (M234EH) and the QA binding pocket (M265IT) and/or increase of the multiplicity of the electron transfer of charge separation in the acceptor side upon mutation.

Original languageEnglish
Pages (from-to)1191-1199
Number of pages9
JournalBBA - Bioenergetics
Volume1827
Issue number10
DOIs
Publication statusPublished - 2013

Fingerprint

Energy Metabolism
Free energy
Fluorescence
Energy gap
Mutation
Dimers
Bacteriochlorophylls
Photosynthetic Reaction Center Complex Proteins
Rhodobacter sphaeroides
Hydrogen Bonding
Bacteria
Hydrogen bonds
Iron
Ligands
Electrons
Proteins

Keywords

  • Bacterial photosynthesis
  • Charge recombination
  • H-bond network
  • Light-induced free energy changes
  • Reaction center protein

ASJC Scopus subject areas

  • Biochemistry
  • Biophysics
  • Cell Biology

Cite this

Mutational control of bioenergetics of bacterial reaction center probed by delayed fluorescence. / Onidas, Delphine; Sipka, Gábor; Asztalos, Emese; Maróti, P.

In: BBA - Bioenergetics, Vol. 1827, No. 10, 2013, p. 1191-1199.

Research output: Contribution to journalArticle

Onidas, Delphine ; Sipka, Gábor ; Asztalos, Emese ; Maróti, P. / Mutational control of bioenergetics of bacterial reaction center probed by delayed fluorescence. In: BBA - Bioenergetics. 2013 ; Vol. 1827, No. 10. pp. 1191-1199.
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abstract = "The free energy gap between the metastable charge separated state P+QA - and the excited bacteriochlorophyll dimer P wasmeasured by delayed fluorescence of the dimer inmutant reaction center proteins of the photosynthetic bacterium Rhodobacter sphaeroides. The mutations were engineered both at the donor (L131L, M160L, M197F and M202H) and acceptor (M265I and M234E) sides.While the donor side mutations changed systematically the number of H-bonds to P, the acceptor side mutations modified the energetics of QA by altering the van-der-Waals and electronic interactions (M265IT) and H-bond network to the acidic cluster around QB (M234EH, M234EL, M234EA and M234ER). All mutants decreased the free energy gap of the wild type RC (∼890 meV), i.e. destabilized the P+QA - charge pair by 60-110 meV at pH 8.Multiplemodifications in the hydrogen bonding pattern to P resulted in systematic changes of the free energy gap. The destabilization showed no pH-dependence (M234 mutants) or slight increase (WT, donor-side mutants and M265IT above pH 8) with average slope of 10-15 meV/pH unit over the 6-10.5 pH range. In wild type and donor-side mutants, the free energy change of the charge separation consisted of mainly enthalpic term but the acceptor side mutants showed increased entropic (even above that of enthalpic) contributions. This could include softening the structure of the iron ligand (M234EH) and the QA binding pocket (M265IT) and/or increase of the multiplicity of the electron transfer of charge separation in the acceptor side upon mutation.",
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