Photoinhibitory Light-induced Changes in the Composition of Chlorophyll-Protein Complexes and Photochemical Activity in Photosystem-I Submembrane Fractions

Subramanyam Rajagopal, Nikolai G. Bukhov, Robert Carpentier

Research output: Contribution to journalArticle

21 Citations (Scopus)

Abstract

The effects of irradiation on photosystem (PS)-I submembrane particles using intense white light (2000 μE·m-2·s -1) at chilling temperature (4°C) were studied. PSI-dependent oxygen uptake activity was stable during the first 3 h of photoinhibitory illumination in the presence of added superoxide dismutase (SOD). Without added SOD, the oxygen uptake almost doubled during this period, presumably due to the denaturation of native membrane-bound SOD or its release from the PSI membranes. The total chlorophyll (Chl) content and the magnitude of light-induced absorbance changes at 830 nm (ΔA830) were also barely affected during the first 3-3.5 h of photoinhibitory treatment. However, further exposure to strong light markedly accelerated Chl breakdown followed by a decline in oxygen uptake rate and ΔA830. This corresponded with the disappearance of the bands attributed to PsaA/B polypeptides on electrophoretic gels. Despite the invariant maximum magnitude of ΔA 830 during the first 3-3.5 h of photoinhibitory treatment, the light-response curves of P700 oxidation gradually altered, demonstrating a several-fold increase in the ability of weak actinic light to oxidize P700. The major Chl a-protein 1 (CP1) band gradually disappeared during the first 4 h of light exposure with a corresponding increase in the Chl content of a band with lower electrophoretic mobility ascribed to the formation of oligomers containing CP1, light-harvesting complex I (LHCI)-680 and LHCI-730. This aggregation of Chl-protein complexes, likely caused by photoinhibitory-induced crosslinking favoring light harvesting, is proposed to explain the enhanced capacity of weak light to oxidize P700 in photoinhibited PSI submembrane fractions compared with untreated ones.

Original languageEnglish
Pages (from-to)284-291
Number of pages8
JournalPhotochemistry and photobiology
Volume77
Issue number3
DOIs
Publication statusPublished - Mar 1 2003

ASJC Scopus subject areas

  • Biochemistry
  • Physical and Theoretical Chemistry

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