title: Direct interaction of the major light-harvesting complex II and PsbS in nonphotochemical quenching.
abstract: The photosystem II (PSII) subunit S (PsbS) plays a key role in nonphotochemical quenching, a photoprotective mechanism for dissipation of excess excitation energy in plants. The precise function of PsbS in nonphotochemical quenching is unknown. By reconstituting PsbS together with the major light-harvesting complex of PSII (LHC-II) and the xanthophyll zeaxanthin (Zea) into proteoliposomes, we have tested the individual contributions of PSII complexes and Zea to chlorophyll (Chl) fluorescence quenching in a membrane environment. We demonstrate that PsbS is stable in the absence of pigments in vitro. Significant Chl fluorescence quenching of reconstituted LHC-II was observed in the presence of PsbS and Zea, although neither Zea nor PsbS alone was sufficient to induce the same quenching. Coreconstitution with PsbS resulted in the formation of LHC-II/PsbS heterodimers, indicating their direct interaction in the lipid bilayer. Two-photon excitation measurements on liposomes containing LHC-II, PsbS, and Zea showed an increase of electronic interactions between carotenoid S1 and Chl states, Φ(Coupling)(CarS1-Chl), that correlated directly with Chl fluorescence quenching. These findings are in agreement with a carotenoid-dependent Chl fluorescence quenching by direct interactions of LHCs of PSII with PsbS monomers.
authors.affiliation: Department of Structural Biology, Max Planck Institute of Biophysics, 60438 Frankfurt, Germany.
authors.forename: Laura
authors.initials: L
authors.lastname: Wilk
authors.forename: Matthias
authors.initials: M
authors.lastname: Grunwald
authors.forename: Pen-Nan
authors.initials: PN
authors.lastname: Liao
authors.forename: Peter Jomo
authors.initials: PJ
authors.lastname: Walla
authors.forename: Werner
authors.initials: W
authors.lastname: Kühlbrandt
mesh_terms: D017360:Arabidopsis; D029681:Arabidopsis Proteins / Q000378:metabolism*; D015153:Blotting, Western; D002734:Chlorophyll / Q000378:metabolism*; D002851:Chromatography, High Pressure Liquid; D002942:Circular Dichroism; D003001:Cloning, Molecular; D004591:Electrophoresis, Polyacrylamide Gel; D045342:Light-Harvesting Protein Complexes / Q000378:metabolism*; D008081:Liposomes / Q000378:metabolism; D018532:Pisum sativum; D045332:Photosystem II Protein Complex / Q000378:metabolism*; D017510:Protein Folding; D011994:Recombinant Proteins / Q000378:metabolism*; D013050:Spectrometry, Fluorescence; D024341:Xanthophylls / Q000378:metabolism*; D065146:Zeaxanthins
chemical_list: D029681:Arabidopsis Proteins; D045342:Light-Harvesting Protein Complexes; D008081:Liposomes; C489731:NPQ4 protein, Arabidopsis; D045332:Photosystem II Protein Complex; D011994:Recombinant Proteins; D024341:Xanthophylls; D065146:Zeaxanthins; D002734:Chlorophyll