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Thylakoid membrane protein phosphorylation modifies the equilibrium between Photosystem II quinone electron acceptors

Authors
Journal
Biochimica et Biophysica Acta (BBA) - Bioenergetics
0005-2728
Publisher
Elsevier
Publication Date
Volume
894
Issue
2
Identifiers
DOI: 10.1016/0005-2728(87)90183-6
Keywords
  • Chlorophyll Fluorescence
  • Electron Transfer
  • Photosynthesis
  • Photosystem Ii
  • Protein Phosphorylation
  • (Pea And Lettuce Chloroplast)
Disciplines
  • Biology

Abstract

Abstract Chloroplast thylakoid membrane protein phosphorylation inhibits Photosystem-II-mediated electron transfer at saturating light intensities. Measurements of room temperature chlorophyll fluorescence have been used to monitor electron transfer reactions between the primary (Q A) and secondary (Q B) quinone acceptors of Photosystem II. The initial transfer from Q − A to Q B is not affected by the phosphorylation, although a second slow reoxidation phase is even slower after phosphorylation. After equilibrium is achieved between Q − AQ B and Q AQ − B there appears to be a higher concentration of Q − A in the phosphorylated membranes. This is explained by a phosphorylation-induced destabilisation of the anionic semiquinone, Q − B, as seen from the DCMU-stimulated fluorescence increase.

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