Characterization of damage to the D1 protein of photosystem II under photoinhibitory illumination in non-phosphorylated and phosphorylated thylakoid membranes

N. Mizusawa, N. Yamamoto, M. Miyao

Research output: Contribution to journalArticlepeer-review

14 Citations (Scopus)

Abstract

Thylakoid membranes retaining a high capacity to phosphorylate the D1 protein of photosystem II but free from contamination by exogenous proteases have been prepared. Almost all the D1 protein in this preparation is unphosphorylated, but it is almost completely phosphorylated by illumination in the presence of ATP. During photoinhibitory illumination of the thylakoid membranes, the D1 protein is cleaved in the DE loop to give rise to C-terminal fragments of 9.3 and 7.9 kDa in both the unphosphorylated and phosphorylated forms, though cleavage proceeds slightly more slowly in the phosphorylated form. Cleavage inside helix D giving rise to a C-terminal fragment of 16 kDa also occurs, albeit to a much lesser extent than that in the DE loop. When samples that have been illuminated with photoinhibitory light are kept in darkness for 2 h, the amount of the 9.3 kDa fragment selectively increases, irrespective of the phosphorylation state of the protein. This cleavage in darkness is not suppressed by protease inhibitors, an indication of the involvement of non-enzymatic reactions. No extra fragments of the D1 protein are detected either during or after photoinhibitory illumination, even when stromal proteins are present. These observations suggest that cleavage of the D1 protein proceeds via the same mechanism in both the phosphorylated and unphosphorylated forms in isolated thylakoid membranes.

Original languageEnglish
Pages (from-to)97-103
Number of pages7
JournalJournal of Photochemistry and Photobiology B: Biology
Volume48
Issue number2-3
DOIs
Publication statusPublished - 1999 Feb 1
Externally publishedYes

Keywords

  • D1 protein
  • Photoinhibition
  • Photosystem II
  • Protein phosphorylation
  • Thylakoid membranes

ASJC Scopus subject areas

  • Radiation
  • Radiological and Ultrasound Technology
  • Biophysics
  • Radiology Nuclear Medicine and imaging

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