title: Significance of molecular crowding in grana membranes of higher plants for light harvesting by photosystem II.
abstract: Significance of molecular crowding in grana thylakoids of higher plants on photosystem II function was studied by 'titrating' the naturally high protein density by fusing unilamellar liposomes of the native lipid mixture with isolated grana membranes (BBY). The incorporation of lipids was monitored by equilibrium density gradient centrifugation and two-dimensional thin layer chromatography. The excitonic coupling between light-harvesting (LHC) II and photosystem (PS) II was analysed by chlorophyll a fluorescence spectroscopy. The fluorescence parameters Fv/Fm and Fo clearly depend on the protein density indicating the importance of molecular crowding for establishing an efficient excitonic protein network. In addition the strong dependency of Fo on the protein density reveals weak interactions between LHCII complexes which could be important for dynamic adjustment of the photosynthetic apparatus in higher plants.
authors.affiliation: Plantphysiology, Institute of Botany, Westfaelische Wilhelms-Universitaet, Schlossgarten 3, 48149, Muenster, Germany. hafers@uni-muenster.de
authors.forename: Silvia
authors.initials: S
authors.lastname: Haferkamp
authors.forename: Helmut
authors.initials: H
authors.lastname: Kirchhoff
mesh_terms: D045342:Light-Harvesting Protein Complexes / Q000502:physiology*; D045332:Photosystem II Protein Complex / Q000502:physiology*; D018521:Plant Physiological Phenomena; D013050:Spectrometry, Fluorescence
chemical_list: D045342:Light-Harvesting Protein Complexes; D045332:Photosystem II Protein Complex