Herbicide binding and thermal stability of photosystem II isolated from Thermosynechococcus elongatus

K. Zimmermann, M. Heck, J. Frank, J. Kern, I. Vass, A. Zouni

Research output: Contribution to journalArticle

32 Citations (Scopus)

Abstract

Binding of herbicides to photosystem II inhibits the electron transfer from QA to QB due to competition of herbicides with plastoquinone bound at the QB site. We investigated herbicide binding to monomeric and dimeric photosystem II core complexes (PSIIcc) isolated from Thermosynechococcus elongatus by a combination of different methods (isothermal titration and differential scanning calorimetry, CD spectroscopy and measurements of the oxygen evolution) yielding binding constants, enthalpies and stoichiometries for various herbicides as well as information regarding stabilization/destabilization of the complex. Herbicide binding to detergent-solubilized PSIIcc can be described by a model of single independent binding sites present on this important membrane protein. Interestingly, binding stoichiometries herbicide:PSIIcc are lower than 1:1 and vary depending on the herbicide under study. Strong binding herbicides such as terbutryn stabilize PSIIcc in thermal unfolding experiments and endothermically binding herbicides like ioxynil probably cause large structural changes accompanied with the binding process as shown by differential scanning calorimetry experiments of the unfolding reaction of PSIIcc monomer in the presence of ioxynil. In addition we studied the occupancy of the QB sites with plastoquinone (PQ9) by measuring flash induced fluorescence relaxation yielding a possible explanation for the deviations of herbicide binding from a 1:1 herbicide/binding site model.

Original languageEnglish
Pages (from-to)106-114
Number of pages9
JournalBBA - Bioenergetics
Volume1757
Issue number2
DOIs
Publication statusPublished - Feb 2006

Fingerprint

Photosystem II Protein Complex
Herbicides
Thermodynamic stability
Hot Temperature
Plastoquinone
Differential Scanning Calorimetry
Stoichiometry
Differential scanning calorimetry
Binding Sites
Titration
Detergents
Enthalpy
Spectrum Analysis
Membrane Proteins
Stabilization
Monomers
Fluorescence
Experiments
Spectroscopy
Electrons

Keywords

  • Binding constant
  • Calorimetry
  • Flash induced fluorescence
  • Herbicide
  • Photosystem II

ASJC Scopus subject areas

  • Biophysics

Cite this

Herbicide binding and thermal stability of photosystem II isolated from Thermosynechococcus elongatus. / Zimmermann, K.; Heck, M.; Frank, J.; Kern, J.; Vass, I.; Zouni, A.

In: BBA - Bioenergetics, Vol. 1757, No. 2, 02.2006, p. 106-114.

Research output: Contribution to journalArticle

Zimmermann, K. ; Heck, M. ; Frank, J. ; Kern, J. ; Vass, I. ; Zouni, A. / Herbicide binding and thermal stability of photosystem II isolated from Thermosynechococcus elongatus. In: BBA - Bioenergetics. 2006 ; Vol. 1757, No. 2. pp. 106-114.
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