Structural flexibility of chiral macroaggregates of light-harvesting chlorophyll a/b pigment-protein complexes. Light-induced reversible structural changes associated with energy dissipation

Virginijus Barzda, Anita Istokovics, Ilian Simidjiev, Gyöz̈ Garab

Research output: Contribution to journalArticle

103 Citations (Scopus)

Abstract

In this paper, we show that stacked lamellar aggregates of the purified chlorophyll a/b light-harvesting antenna complexes (LHCII) and granal thylakoid membranes are capable of undergoing light-induced reversible changes in the chiral macroorganization of the chromophores as well as in the photophysical pathways. In granal thylakoids, the light-induced reversible structural changes, detected by circular dichroism (CD) measurements, are accompanied by reversible changes in the fluorescence yield that indicate an increased dissipation of the excitation energy. These changes become gradually more significant in excess light compared to nonsaturating light intensities, and can be eliminated by suspending the membranes in hypotonic, low-salt medium in which the chiral macroaggregates are absent. In lamellar aggregates of LHCII, the light-induced reversible changes of the main, nonexcitonic CD bands are also accompanied by reversible changes in the fluorescence yield. In small aggregates and trimers, no light-induced ACD occurs, and the fluorescence changes are largely irreversible. It is proposed that the structural changes are induced by thermal effects due to the excess light energy absorbed by the pigments. Our data strongly suggest that the structure and function of the antenna system of chloroplasts can be regulated by the absorption of excess light energy with a mechanism independent of the operation of the photochemical apparatus.

Original languageEnglish
Pages (from-to)8981-8985
Number of pages5
JournalBiochemistry
Volume35
Issue number27
DOIs
Publication statusPublished - Aug 2 1996

ASJC Scopus subject areas

  • Biochemistry

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