A1 Refereed original research article in a scientific journal
Protein phosphorylation and magnesium status regulate the degradation of the D1 reaction centre protein of Photosystem II
Authors: Rintamaki E, Salo R, Koivuniemi A, Aro EM
Publisher: ELSEVIER SCI IRELAND LTD
Publication year: 1996
Journal: Plant Science
Journal name in source: PLANT SCIENCE
Journal acronym: PLANT SCI
Volume: 115
Issue: 2
First page : 175
Last page: 182
Number of pages: 8
ISSN: 0168-9452
DOI: https://doi.org/10.1016/0168-9452(96)04343-9
Abstract
Illumination of higher plant leaves (pumpkin, wheat and pea) at a photon flux density of 1200 mu mol m(-2) s(-1) induced strong phosphorylation of the D1 reaction centre protein of photosystem II. Phosphorylation of D1 protein was not observed in a moss Ceratodon purpureus. To study the effect of protein phosphorylation on D1 degradation, thylakoids isolated from pumpkin leaves and Ceratodon were phosphorylated in vitro in the presence of ATP before being subjected to photoinhibitory illumination. The rate of photoinhibition of Photosystem II oxygen evolution was not influenced by phosphorylation conditions in pumpkin or Ceratodon thylakoids. D1 protein in its phosphorylated form in pumpkin thylakoids was degraded significantly more slowly whereas in Ceratodon the degradation of D1 protein occurred rapidly with or without the presence of ATP in the photoinhibitory medium. Depletion of Mg2+ ions also blocked the degradation of unphosphorylated D1 protein in pumpkin thylakoid membranes. We conclude that degradation of the D1 protein in higher plants is regulated by phosphorylation on the substrate level and its optimal rate requires the presence of Mg2+.
Illumination of higher plant leaves (pumpkin, wheat and pea) at a photon flux density of 1200 mu mol m(-2) s(-1) induced strong phosphorylation of the D1 reaction centre protein of photosystem II. Phosphorylation of D1 protein was not observed in a moss Ceratodon purpureus. To study the effect of protein phosphorylation on D1 degradation, thylakoids isolated from pumpkin leaves and Ceratodon were phosphorylated in vitro in the presence of ATP before being subjected to photoinhibitory illumination. The rate of photoinhibition of Photosystem II oxygen evolution was not influenced by phosphorylation conditions in pumpkin or Ceratodon thylakoids. D1 protein in its phosphorylated form in pumpkin thylakoids was degraded significantly more slowly whereas in Ceratodon the degradation of D1 protein occurred rapidly with or without the presence of ATP in the photoinhibitory medium. Depletion of Mg2+ ions also blocked the degradation of unphosphorylated D1 protein in pumpkin thylakoid membranes. We conclude that degradation of the D1 protein in higher plants is regulated by phosphorylation on the substrate level and its optimal rate requires the presence of Mg2+.
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